Butt,
Most of the books readily available are lightweight in the performance area and of very limited use. Those which are most of use are specialist and not available in the retail market.
If you can sidestep the maths, you might like to look at
(a) Aircraft Performance, Mair and Birdsall, Cambridge Aerospace Series, ISBN 0-521-36264-4 or 0-521-56836-6
(b) Theory of Flight, Von Mises, Dover, ISBN 0-486-60541-8.
Neither is directed at pilots and omit pilot useful data, but each is eminently readable.
Von Mises is quite ancient and of use more for background reading. No doubt you will find others around in the tech book shops.
Otherwise try an aero eng university library. You are likely to find such gems as Boeing's Performance Engineer Training Manual (otherwise known as Jet Transport Performance Methods - D6-1420), the AGARD Flight Test Manual, and other flight test training documentation, from ETPS, USNTPS and similar.
[This message has been edited by john_tullamarine (edited 25 June 2001).]