B is for Bitcoin is the very best first book for anyone interested in Bitcoin. 
Written by @daz and @sebbunney 
It’s concise and covers everything to help someone understand what Bitcoin is and how it works. It is a quick read especially for a smart person and it’s detailed enough to open the door to the next books. In fact I think you’d find they would start actively seeking out info on their own after as they will have a good grounding in the fundamentals.