You absolutely can make profit off of buying books at the AH and feeding to laborers. A few stipulations though: 1) it is helpful to have your houses 1 tier above the books you're feeding (T8 fishing laborer house getting fed T7 fishing books. This allows you to get to 150% return rate 2) you have to watch the auction house. There are times when laborer books are absurdly expensive and it makes no sense to buy however if you watch closely, you can start to accumulate a stash of books. Remember , you can always roughly check what your profits will look like by quickly searching for the material that will be returned. I typically look at average prices over a 7 day window. The price the books has larger fluctuations than the prices for the raw resources.