I am looking for a fantasy book:
What I vaguely recall is:
A boy is sick with the root cause being magic within himself. He is semi-cured by someone and is told he needs to train with the wizards in the towers throughout the land. He finally decides to leave his family and train at the towers. I am pretty sure each tower in the land held different responsibilities, and someone or something was tearing down the towers in the lands.
The book was in English. I was thinking it was written in the 80's or 90's. This book was picked from old books people donated to the military (so it certainly wasn't "new"). This was a full book, not a short story, and I recall that it was part of a series: at least three books, probably more. The cover had some orange tint to it, and pictured a castle/tower in the background to the left side, while in the foreground there was a person riding a horse along a winding trail to the tower/castle.
Any help would be appreciated. This is not the Seventh Tower Series.