Rich Dad Poor Dad - What the Rich Teach Their Kids About Money - That the Poor and Middle Class Do Not! by Robert Kiyosaki was the very first book that inspired me to go about working and investing a different way than what is ordinarily accepted in our consumer-debt driven society.
It's an easy read, and a great way to start seeing life from a different perspective. Check out my friend, Trevor's blog here to read a great review on the book's concepts and ideas.
And remember to take these books and ideas in as a guiding force, not as the "end all be all". The way you acheive your wealth will undoubtedly vary, but why not study from some of the best mentors out there?