One of the beauties of living here is you can grow your own herbs, food and flowers year 'round -- and landscape your home yourself. (There are classes at Miami Dade College, Fairchild Tropical Gardens and the University of Florida Agricultural Extension office in the Redland addressing these interests as well as specializations like growing mangos, palms or your own organic vegetable garden.)
Our climate and soil are unique within the U.S. -- we're in our own climate zone -- and even the soil in the Keys is different from ours. This means the gardening and plant-growing needs in our area are different from the needs of those living north of Palm Beach County.
The books I use for reference in gardening are thin and generally published by the University of Florida Press (this is too small a market for regular publishers). Consequently, even in paperback, they can cost as much $35.
At the library, these books are usually kept in the reference section, therefore not available for check-out. So gardeners want their own copies. Happily, the book fair makes these books affordable.
The University of Florida Press always has a booth during the street fair. If you shop their distressed section, you can often get those books for one-third to one-fifth of the cover price because it has a creased page or a roughened edge.
The best time to shop for any books at the fair is late Sunday, assuming you're willing to risk the vendors being sold out of what you're seeking. Many sellers do not want to pack up and move their inventory, so they start promoting different bargain.
As I recall, UF does not. The Press' only discounts are on damaged books, so don't wait to seek them out. Then again, sometimes books are accidentally damaged during the event so you may get lucky at any time.