Here are a couple of threads that might help - loads of info from loads of folks (some of who aren't around here any more to share their knowledge):

http://www.themodernantiquarian.com/forum/?thread=24657

http://www.themodernantiquarian.com/forum/?thread=45541

Plus Jane's weblogs saying what we saw when we went a couple of years ago:

Hot stuff in Aberdeenshire: the pleasure and the pain:
http://www.themodernantiquarian.com/post/48981/weblog/

Hot stuff in Aberdeenshire: fried brain overload:
http://www.themodernantiquarian.com/post/48971/weblog/

Hot stuff in Aberdeenshire: stone-baked:
http://www.themodernantiquarian.com/post/48959/weblog/

There's so much to enjoy, I feel privileged to have been able to visit so often! :^D

Bookswise, other than Julian's TMA & Burl's 'little' book (& the big one if you've a big rucksack), I never really found any myself, as I never got round to writing one! ;^)

I'd recommend spending the money on maps instead. Most are fairly easy to find & I managed ok with Landrangers, but Explorers would make a few of them easier to find!

There's a RCAHMS book coming out but may be too late for you discussed here http://www.themodernantiquarian.com/forum/?thread=50296

It was supposed to be out this month I think but according to Amazon & Waterstones, it's been delayed until June next year.... :^( http://www.waterstones.com/waterstonesweb/displayProductDetails.do?sku=6276665

love

Moth