Unfortunately, it seems like they all have the same title 😉
- Fretless Bass – Without Frets without limits 1 by Ralf Gauck
Good structured exercises with useful tips on fingerings and and a good guide to decent vibrato technique (german read)
- Fretless Bass – Without Frets without limits 2 by Ralf Gauck
not read yet, but i guess it’s as good as part one
- Fretless Bass – The Ultimate Fretless Bass Workout by Steve Bailey
A lot of stretching exercises, fun is coming in the second half
- Fretless Bass by Chris Kringel
Instructional book but also with full song transcriptions
- Fretless Bass by Bunny Brunel & Josquin des Prés
- 101 Bass Tips – Stuff all the pros know and use by Gary Willis
Mostly general bass tips but also some specially for fretless. I whould definitely like to read more about fretless from Gary Willis.
- 100 Fretless Bass Workouts by Chris Matheos
This book is just a collection of exercises with barely any explanation. Even key elements like fingerings are missing. In my opinion it only makes sense as an additional workbook for another method.
- The Fretless Bass by Chris Jisi
Interviews, discography, gear and lessons with 25 fretless bass greats – good read for starters
- Truefire Course – Fretless Bass Foundations with Tony Franklin
A great course for starters with usefult tips and motivation from Tony. Contains musical and fun intended exercises
- Scotts Bass Lessons
There are two good fretless courses at Scotts Bass Lessons. One with Steve Lawson, which is available for paying SBL members, and one external class with Gary Willis, contains interesting information and stunning performances by Gary. That one is not always available, but they offer the course from time to time.