Well try this AMAZON link

http://www.amazon.com/Expert-Systems-Artificial-Intelligence-Books/b?ie=UTF8&node=3890

dear Theodora, i want your suggestion about this matter....

I would suggest the following:

[1] Introduction to Expert Systems, Jackson P. , 3rd edition, Addison Wesley, ISBN 0-201-87686-8

[2] Giarratano J. , Riley G. , Expert Systems, Principles and Programming, PWS Publising Company, Boston., ISBN 0-534-93744-6

But, one of the most advanced ones is the following:

[3] Introduction to Knowledge Systems, Stefik M., Morgan Kaufmann, ISBN 1-55860-166-X

Thanks Nick for that ... well, this one seems ok - but might be a bit expensive - however, there is kindle version - and published by Springer

Recommender Systems Handbook edited by Francesco Ricci, Lior Rokach, Bracha Shapira, and Paul B. Kantor

Hope this helps!

Regards

Theodora Issa

Thanks Dear Nick,