Best books for realtors

[Ken Mucha]

My goal is to read 1 book every quarter. What are some great books to read to help my investor clients and to assist me in gaining knowledge and grow as a realtor?   In addition, I would prefer a digital copy instead of a hard copy.   Two part question.  1) What are the best digital options to read from my cell phone?  2) I would like to have multiple agents (3-5) in my office have access to this digital copy to read as well.  Is there way to do this?