1. The War of the Worlds:

The war of the worlds is one of the progenitors of the sci fi genre. It popularized a particular kind of alien invasion story that has been mimicked and iterated on for ages. The story is compelling, if a bit shallow in the character writing department. But equally importantly it is a fascinating look into the origins of the Sci Fi genre.

2. Enders Game:

Ender's game is a book that it is probably safe to call a classic at this point. With a fascinating world, intriguing characters and conflicts, Ender's Game is a thrilling ride all the way through. The drama and intrigue will keep you hooked from cover to cover, and the sci fi action helps to balance out the brutal world.