The most useful [rather than best] Buddhist Book I read in 2012 was Buddhadhasa Bhikkhu’s The Buddha’s Doctrine of Anatta:A Comparative Study of Self and Not-Self in Buddhism, Hinduism and Western Philosophy.
Originally written in 1939 in Thai, an English translation was produced in 1990 in Thailand. It was reproduced in The Collection of Buddhadhasa’s Long Writings but that book is rare.
It can be a quick read, done in a day, but it’s a little better to take one’s time over it to absorb some of the finer points the author makes. Anatta is not that complicated to understand if we can remove some of the misunderstandings that get introduced from other sources. That is the whole point of the book.