Let me state right of the bat that this book is head-deep in psychoanalytic terminology and to me represents the best confrontation (way better than anti-oedipus and a thousand plateaus) of Deleuze's philosophy with psychoanalysis. I think many readers of Deleuze get caught up in Deleuze's originality and forget that he didn't try to describe a completely new system of everything, but rather wanted to describe more precisely the logic of a creative ontology. For a serious critique of psychoanalysis, the logic of sense is the book to go to, not anti-oedipus. It is for this reason - his desire to confront lacanian psychoanalysis head-on that I consider this to be his boldest book.
Also let me mention that it is in the appendix of this book that Deleuze deals with an extremely important problem which is almost completely overlooked by most Deleuze scholars - the problem of the other. This problem is inextricably linked with lacanian psychoanalysis and hence any critique of psychoanalysis must rigorously understand the ontology of the other. Deleuze here says that the ontological status of the other is that of a "possible world" which complicates things a bit because of his earlier critique of the concept of the possible in difference and repetition.
In contrast to one of the previous reviewers, I consider the idea that Deleuze is or was ever a post-semiotic theorist is completely wrong. In many interviews when asked about what he tried to do, he answers that he tried to come up with a theory OF signs (this is even his answer after he worked with guattari, which is very curious)... This is evidenced quite clearly in that one of his earliest books is on proust and signs, and that in Difference and Repetition, signs repeatedly come up as being the "flashes" as Deleuze describes them, that connect intensive differences. A book coming out called "the primacy of semiosis" uses a synthesis of Deleuze's ideas about univocity and signs with other theorists and will probably provide useful reading for this problem.
You can certainly read this book for fun, but I think the more "fun" of Deleuze's books are the works with Guattari, which I am sorry to say, are also his worst books. All of the genius in them (mostly stylistic, not conceptual) relies on the genius of his early work (the concept creation). The concepts were created very early, and as Badiou claims, Deleuze just found different names for them in different contexts. Not to bash Guattari, I think his "Three Ecologies" is quite good (not his earlier stuff though), but the combined work is more interesting than it is philosophically serious. lets not forget something quite crucial: Deleuze states guattari saved him from psychoanalysis - which is why this book is so important since it is the only and last confrontation Deleuze ever has WITHIN psychoanalytic terminology.
Again, I can't stress it enough, to understand this book, you need to read Lacan since much of the book is most obvioiusly a response to and a re-internalization (through "buggery") of lacan (the chapter titles make this quite obvious).
I also recommend as a supplement to this:
1) The Lacanian Subject - by Bruce Fink... Incredibly clear book on lacan's theory of the subject.
2) Difference & Repetition (Deleuze's Masterwork)
3) The Anti-Oedipus papers: Deleuze and guattari's letters to each other in the production of anti-oedipus. Here the problems become more obvious and the genesis of the style explicit.