This book of studies (compiled by Donald Reinhardt) starts off with simple studies for the beginner that are also useful as long tone exercise pieces for the advanced student or professional.
It then progresses to more challenging keys and more complicated figures. All in all the 15 studies are definitely "tuneful" rather than mechanical.
All studies are notated in bass clef, with an emphasis on the upper range (above middle C) just right for tenor trombone.