Amit, The specification is quite important if you want to score well. Besides scoring well, it is also important if you want to learn EJBs well. They are not just for providers but for developers as well. Having said that, it is not necessary to read the specs from cover to cover. You can do a selective reading. For example, chapters on JPA, JPQL, Exception handling are very important.
BTW, do not get put off by size of the specs. They are quite easy to understand once you start reading them.