Note: Fake, prop books used in the show are not included in this list.
Episode 1: "Work That Body for Me"
Piper: Funny Girl by Nick Hornby
Yoga Jones: High Fidelity by Nick Hornby
Episode 2: "Power Suit"
Black Cindy: What Makes Sammy Run? by Budd Schulberg
Red: My Beautiful Ballooning Heart by Janice Silverman Rebibo
The rest of the books in the pile seem to be prop books.