As Dan have already pointed out, free publicity can sometimes pay off far better then a payed job. I cant tell you what to do here, but two things to keep in mind is contract and copyright. ALWAYS sign a contract, and most important of all, make sure that the contract clearly say that YOU hold the COMPLETE copyright for the images used. Since hes asking you to work for free, he really cant refuse on this part.(payed commissions is another story) Also make sure to get credit for the image in the book. As for the pricing, its probably one of the most difficult things, and setting the right fee is far from easy. However, based on own experience, a serious client will not get scared away simply by a suggested fee. 9 times of 10, they will get back to you, telling its slightly out of their budget, and suggest a lower fee. Good luck what ever you decide. :)

Rudolf Herczog
Digital Artist
www.rochr.com