I test my winboard chess engine Nameless with gauntlet matches in Arena GUI using some epd starting positions. As I was looking for a way to use GUI books I searched the Arena website. In playwitharena>Home > Tips + Tricks > Engine Tournaments I found the following in the last paragraph of Engines configuration section:
In opening books, the first moves of a game are saved. Many engines use their own books, which are often tailored to the game style of the engine. There is also the possibility to use so-called GUI books, in doing so the engine does not decide about the first moves but the GUI. (translation)
So I opened Arena GUI, entered book>manage>data, selected Arena\Books\Perfect_2010.abk, pressed "load", ticked all the boxes and started the gauntlet match with default starting position. My engine as well as the sparring partners insisted on searching for the opening moves.