Xarra, welcome to WriteWords, and congratulations on the offer.
To be honest, I'm not sure about a deal like that for a photobook, though a 10% royalty is very standard. What you think of any deal depends on the size of the publisher and the market, and the cost of producing and distributing the books. Put it this way: for a little independent press that might be an excellent offer, for a big house it wouldn't be at all.
One thing to be absolutely sure about is what the situation is with copyrights - do you keep them? Does the publisher control the rights (and get a cut or all of the payments?) to print and reproduction or do you? What's the deal if the books are remaindered or go out of print? And if it goes into paperback? And so on.
You could try asking the Society of Authors, who have a legendary contract-checking service for members: you've been offered a contract so are eligible to join. I would certainly suggest that you get the contract checked out by someone.
http://www.societyofauthors.org/index.html
Alternatively the photographer's bodies may do similar things. You probably know more about them than I do, but these are two who I know of:
http://hub.the-aop.org/
http://www.bipp.com/
Very good luck. I do hope it works out.
Emma