I have been watching this question for sometime, because the original poster posted this question in response to a comment I made earlier. I have refrained from replying because I didn't feel I could do justice to the Lotus Sutra, especially without coming across as attacking Theravada Buddhism.
However, given that Saptha Visuddhi above have decided to attack the Lotus Sutra and Mahayana Buddhism, I feel I must correct these erroneous views.
First of all, I must state that, in contrary to common Theravada claims about being the 'Pure Tradition' handed down by the Elders, Theravada is not the same as the Buddhism taught during the time of the Sakyamuni Buddha. Indeed while it is the most conservative, but it is not 'pure'. A common narrative asserted by the Theravada was that they maintained all the teachings handed down since the Early Buddhist Council, and maintained that they are descended from the Sthavira sect, while Mahayana are Mahāsāṃghika. Theravada narrative assert that the Mahāsāṃghika split off from the elders because they want to modify the Vinaya. While historical evidence and the narrative of other schools indicate that it was in fact the Sthavira who wanted to add more rules to the Vinaya. Never the less, the current surviving Vinaya of the Mahayana traditions (East Asian and Tibetan) are in fact also descended from the Sthavira, and has more monastic rules than what is scholarly accepted to be the oldest the Mahāsāṃghika.
Further more, the Abhidhamma according to Theravada narrative asserts that it was taught by the Sakyamuni Buddha to his mother in heaven. This should have indicated that skillful means was being employed on the origins of this teaching. Historical scholars indicate that the Abhidhamma as a synthesis of the Buddha's teachings, and has a checkered history and was not accepted by all Buddhist schools, and were actually one of the reason for the Early Buddhist schisms as each schools reject or accepted the metaphysical doctrines of other schools. Indeed some Buddhist sect did not consider Abhidhamma to be canonical at all as originally the teachings were called Dharmavinaya, containing only two 'baskets'.
The Abhidhamma made a lot of metaphysical assertions, as the teachings of the Buddha were analyzed and compiled. Prophetic predictions were made about the coming of the Future Buddha Maitreya, the disappearance of the Dharma and so forth. The differences between Buddhas and Arahants, and indeed the Four Stages of Enlightenment were analytically described. These four stages would have originally correspond to having attained Right View to practice the Noble Eightfold Path (stream entry), Ethics (Once Returner), Concentration (Non Returner), culminating in the Wisdom of a perfect Arahant. The differences between a Buddha, an Arahant, an a Pratyekabuddha were further described. In fact, many of these metaphysical doctrines made their way back into the Sutta Pitaka.
Scholars, however, generally date the Abhidhamma works to originating some time around the third century BCE, 100 to 200 years after the death of the Buddha. Therefore, the seven Abhidhamma works are generally claimed by scholars not to represent the words of the Buddha himself, but those of disciples and scholars.
According to Keown, "there is considerable disparity between the Pāli and the Sarvāstivādin versions, with more than two-thirds of the sūtras found in one but not the other compilation, which suggests that much of this portion of the Sūtra Piṭaka was not formed until a fairly late date."
This is a heterogeneous mix of sermons, doctrines, and poetry attributed to the Buddha and his disciples. The contents vary somewhat between editions. The Thai edition includes 1-15 below, the Sinhalese edition 1-17 and the Burmese edition 1-18.
However we can begin to see some common controversies and problems that exist to this day. For example, the nature of Nirvana, the nature of the discrete states of enlightenment. And the nature of prophecies. The role of women. The role of Arahants. How many times have you seen Buddhists passively accept the decline of the Dharma because it was already foretold by the prophecies. I have even seen Theravada Buddhists stated that in this Degenerated Dharma age, no one can attain Arahantship and that the best bet is to hope for rebirth in the time of the Maitreya and become enlightened then. The passive fatalistic world view was threatening the survival of Buddhism itself. Indeed even Sri Lanka, the very heart of Thervada Buddhism has demonstrated, they have actually lost the Dharma transmission at least 3 times in their history and had to be revitalized from else where.
Further more, certain schools such as the Madhyamaka led by Nagarjuna utilizing the doctrine of dependent origination, logically show that because all phenomena are dependently originated, they are ultimately empty, that is impermanent and selfless. Hence in Nirvana there is no actually leaving to go anywhere. As the Buddha would say the five aggregates are impermanent and not self.
Eight Negations Of Nagarjuna
This probably imply in my own opinion to mean that there is no permanent cessation of birth and death. The cessation of suffering and sankhara are impermanent.
Hence, the ideal of the Bodhisattva was born, instead of desiring to be free from all worldly attachments as soon as possible, Buddhist monks and laymen alike were exhorted to remain engaged with the larger society. If escape from Samsara was in some sense impossible, what then is the goal of the Buddhist life?
The Lotus Sutra is one of those text which laid out the purpose of Buddhism. It points out that ultimately there is only One Vehicle, not three distinct vehicles, The Savakas, Pratyekabuddhas, Bodhisattvas are ultimately on the same path - the Noble Eightfold Path. While there are differences in relative abilities, they are not ultimately irreversibly separated from one another. The teachings are only different because the abilities of people to understand something is different. Skillful means was emphasized as the manifold ways which a Buddha can teach sentient beings the Dharma. This was demonstrated with the parable of a rich man with the burning house who attracted his children out of the house by promising the rewards of different carts, but when they ultimately leave the house, the real cart "the one vehicle" they received is even more beautiful than the promises. The Lotus Sutra overturn the metaphysics described in the Suttas and emphasized that they are only skillful means, that is metaphors for the holy life.
Further more, Nirvana is compared to a phantom city magically conjured in the desert, allowing weary travelers searching for treasures to rest. Because the spiritual life is so difficult and demanding, nirvana allowed them to rest, before being exhorted to go further to the true purpose of the practice, to attain enlightenment. That is the Lotus Sutra state the goal of Buddhist practice is not to merely attain the state of no suffering, but to attain the full wisdom of a Buddha. This was compared to another parable where a runaway son returned home but did not recognize his own father, and the father set him out to do simple tasks at first to instill confidence until he can fully take on the inheritance of his father himself. Hence all beings have the potential to become a fully enlightened Buddha, regardless whether they are women, non humans or even sinners like Devadatta.
Further more, the Buddhas themselves are described as immortal because the True Dharma is immortal, unconditional and always present, the Noble Eightfold Path will always be the universal gate to experiencing Awakening.
This is reemphasized in the Universal Gate Chapter of the Lotus Sutra, said to be the very heart of the Lotus Sutra and a focus of many Mahayana Buddhist school. In it, it is stated that Avalokiteshvara Bodhisattva can save beings who call upon him from the dangers fire, flood and storm, knives, demons, chains and demons. The dangers are of course the fire of anger, flood of cravings, storm of delusion, the knives of conceit, the demons of temptations, the chains of attachments and the robbers of afflictions, and we will indeed be saved as long as we apply the Dharma compassionately. The Avalokiteshvara is further stated to be able to transform to whatever beings as needed to teach the Dharma, reminding us that the Dharma is present everywhere if we knew how to look. The finger is not the moon, the raft is to ferry us across, not to be carried after we have arrived.
If you are attached to the metaphysics of Theravada Buddhism, you will be unable to see the wisdom within the Lotus Sutra.
I recommend reading this as a good introduction: