A personal belief of mine is that mathematics should not be mysterious. Some mathematics is very easy to explain. However, a few branches of mathematics are truly hard; among them are algebraic geometry and derived categories. My moral goal in this book is to demonstrate that the theory of derived categories is difficult, but not mysterious.
The [EGA] series by Grothendieck and Dieudonné, and then the book [Har] by Hartshorne, have shown us that algebraic geometry is difficult but not mysterious. The definitions and the statements are precise, and the proofs are available (to be read or to be taken on trust, as the reader prefers). I hope that the present book will do the same for derived categories. (Although I doubt I can match the excellent writing talent of the aforementioned authors!)