Best Book to learn Celestial mechanism?

I’m tried “Fundamental Astronomy” and “Astronomy Principal and Practice” etc but none of them has satisfying explanation,lots’s of unnecessary confusion where its clearly possible to explain in a better way.
Even sometimes it has mistakes that makes thing more and unbearably complicated.
I’m on intermeddiate level and I need a resource so that I can learn The topic more satisfyingly.
Especially for IOAA.

Any other resources beside would be accepted as well