There’s no way to ask that question without sounding pushy, sorry, especially with a coworker. If you give a book to someone as a gift, they have no obligation to read it, and pestering them to give you a review because you want it is rude. This is especially true if it’s only been a few days since you gave it to them, sheesh.

I speak from experience here. A coworker once insisted on lending me a video I had no interest in watching and then proceeded to ask me every single day if I’d watched it yet. I just started avoiding him and gave him back the video after having read enough about it on Wikipedia to get him to leave me alone about it already.