This is a classic Bildungsroman -- one of those wonderful books that allows the reader snapshots into the protagonist's life as he grows from a child into a man. Because of the nature of such novels, I found the beginning of the book quite tedious and uninteresting. In fact, it wasn't until about page 300 (when Phillip Carey, the novel's subject, is in Paris) that I felt I was really "hooked" on the story. After that point, however, I found it enjoyable to put the pieces together in the book, and to figure out how Phillip's childhood and strange adolescence made him into the man he became.
The one piece of the puzzle that never quite fit in is Mildred, the rather disgusting object of Phillip's obsession. At first, I kind of liked her for her cheekiness. As Phillip's passion for her grew, however, so did my distaste for her -- I found myself muttering warnings to Phillip under my breath each time he extended himself to her. Mildred is a unique character, however, simply because she's revolting; I didn't expect her to become so prominent in Phillip's life, because I always anticipated he'd be attracted to someone kind and lovely (like a Thomas Hardy female character). She is just one of many interesting twists in this book.
I also really enjoyed the "motherly" theme of the book. Phillip's journey through life begins without a mother, he inherits an inadequate aunt as a mother-figure, he encounters a passionless mother in Mildred, finds admirable and pitiable motherly qualities in Mrs. Athelny, and ends up with a woman who is always described as "maternal." I found it interesting to follow that thread throughout the book.
I was surprised by the ending because it didn't really seem to fit in with the rest of Phillip's life. However, upon re-reading the section of Phillip's "epiphany" about life, it all seems to work out correctly.