for me it was a real musical education - especially for tunes that were a little bit out of the mainstream and that had good changes in the Real book - like "Where Are You," "You Are Too Beautiful," "I Should Care" - particularly if one compares them to the original sheet music changes; first of all, by looking at the original sheet music one has a better idea of what the original composer intended and one can build from there - as Monk did on many occassions - on the other hand, it always fascinated me that Monk himself frequently stayed near the original sheet music changes - listen to his solo Columbia version of Dinah - where a typical modernist would look to reharmonize the A section (adding probably 2 and 3 minor subs) he stays on the F like an old-time pianist - which in many ways I think he was (even his version of stride sounds more like a '30s ragtimer than it does like James P.) - also on the Monk/Rollins version of More Than You Know, he resists the temptation to play a 2-5 in the third measure of the melody - my point in all of this is that the Real Book was, for me, an eye-opener on how jazz players use harmony, especially in relation to the original music -