Additionally, because this f*ing group was deleted, here is a book list from a post from the last group from someone who passed section 4.
Professional Practice of Landscape Architecture (Rogers)
Site Analysis (LaGro). Absolutely mandatory for Section 2.
Basic Elements of LA Design (Booth) . Also a good refresher, some chapters are relevant for Sections 1 and 3. It's a good academic reminder for things like texture, color, space, form, that you may not discuss as often during daily office work.
Landscape Planning: Environmental Applications (Marsh). This is a VERY useful book. I don't know why it isn't on the "official" lists, it should be. Buy this book! Especially for Sections 4 (and 3, and 2)
TSS
LA Graphic Standards (Hopper). Some is repetitive compared to TSS, but it is not all the same material, so if you're going to take all 4 sections, you may as well add it.
Site Engineering for Landscape Architects. 100% necessary for Section 4. I did not use the accompanying workbook (additional, must purchase separately), but one of my coworkers found it very helpful.