Although book stalls can be hard to come across inside Chatuchak Market, there are stalls selling hundreds of books. The stalls have books in many languages from around the world and many are very cheap as they are pre-owned. The range of books is vastly ranging from the latest number one best-seller to 100-year-old ancient history, the stalls will surprise you with the depth of their literature. Western and Asian classics are readily available and, if you want something in particular ask the stall holder if they have it. If they don't, they may be able to point you to the right stall that sells the book you're after. Should you feel there may be a language barrier, write down the name so you get exactly what you want.
The book stalls at Bangkok Market also sell stationery, so if you're looking for a new notebook or diary, you should be able to find something quite unique. Some stalls will also sell stationery in bulk so getting personalised office materials for a company can be sent back to your home address or workplace.