Yes, there are!
I can recommend a number of great marketing books - basically anything by Seth Godin (including Purple Cow, and the books in that 'series') is superb and well worth the read.

I'm sorry I don't have much personal insight to offer on VA specific books but maybe someone else will jump in here with a recommendation for you.

Amazon has a reviews system too so you can go look up a look and then scroll down the page to see what others have said about a particular title.

Good luck

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