The drug was one of many developed by chemist and psychedelics researcher Alexander Shulgin. As with hundreds of other compounds, the chemical structure and effects of this new drug are described in the book.
From the experiences of testing this compound, it seems 4-TASB was not a success:
Music was lovely during the experiment, but pictures were not particularly exciting. I had feelings that my nerve-endings were raw and active. There was water retention. There was heartbeat wrongness, and respiration wrongness. During my attempts to sleep, my eyes-closed fantasies became extremely negative. I could actually feel the continuous electrical impulses travelling between my nerve endings. Disturbing. There was continuous erotic arousability, and this seemed to be part of the same over-sensitivity of the nervous system; orgasm didn’t soothe or smooth out the feeling of vulnerability. This is a very threatening material. DO NOT REPEAT.
Link to 4-TASB entry from online PiHKAL.