In reply to RossKirtley:
There is no 'best' guide, there is only what suites you for each visit.
My favourite guide is the "Off-Piste", but it's perhaps not ideal for a first visit.
The Jingo-Wobbly guide has it's own style, but its probably better for the lower grades.
The 'purple' guide is probably best for a first visit - though it is probably not 'the best guidebook'. Then there are tens of others.
Part of the fun of Font, though, is just turning up in an area and climbing (especially on a first visit). This is particularly relevant if you've never been before, as the grades will make no sense at all. I used to flash 'Font' 6b/+ regularly in the Peak District, and tick 6c/+ without too much hassle. Yet I struggle desperately to climb 6a in Fontainebleau itself!
Don't forget- "for every grain of sand on the sole of your shoe, add one grade of difficulty to the problem"!