• The Fretless Bass by Chris Jisi
    Interviews, discography, gear and lessons with 25 fretless bass greats – good read for starters
  • Fretless Bass – The Ultimate Fretless Bass Workout by Steve Bailey
    Mainly exercises
  • Fretless Bass by Chris Kringel
    Instructional book but with full song transcriptions
  • Fretless Bass by Bunny Brunel & Josquin des Prés
    Instructional book
  • Fretless Bass – Without Frets without limits 1 by Ralf Gauck
    Mainly exercises with useful tips on fingerings and , german read
  • 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.

Unfortunately it seems like they all have the same title.

Online Courses

Not exactly books but good and entertaining instructional material though.

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 course with Gary Willis, that also contains interesting information and stunning performances by Gary. That one is not always available but they offer the course from time to time.