As a professional bassist and saxophonist, I’ve worked through many books on techniques for both instruments. Saxophone technique books typically favor solo vocabulary and guide the player towards developing this facility. I've found that many books on bass playing don't direct the player towards creating this particular skill. Danny Ziemann's Topics in Jazz Bass, Volume 2: Soloing shines a light into a bass player's world that has remained relatively unseen by those bassists who haven’t doubled on a “melody” instrument.
There is a section explaining guide tone lines in Ziemann's book. This is an important concept for the bassist to grasp, as it guides the thought process away from the bass player’s default setting of “playing roots." He presents a melodic progression from a lead-instrument's view, flipped upside-down from the bassists’ usual subterranean perspective. In explaining this concept, Ziemann has presented the material in a way that the bassist’s mind and ear are trained before the hands: read, hear, sing, play. Once this concept is presented, Ziemann provides exercises to develop that link between the ear and hands. The exercises are not difficult for an intermediate to advanced player, yet they provide a challenge in fingerboard/hand-eye-ear coordination. Once the player has committed them to music-memory, their instant recall will be invaluable in framing a structure for meaningful solo lines.
Much like a saxophone method book teaching the vocabulary of Bird or 'Trane, this book introduces similar lines for the bass player—written in all keys. This is valuable. Personally, over the years I have become frustrated with books presenting a concept in one key, then suggesting moving it to all keys without further ado. Volume 2: Soloing presents the concept in a way that the player can see and sense the differences in each key. The written note choices reflect differing positions on the fingerboard that are best suited for each passage.
While all of the concepts presented in this book are tangible and important, in my opinion the most valuable part is Ziemann's explanation of how to transcribe. We’ve all been told over the years to “just listen to the song and transcribe the parts,” but little has been taught about transcription techniques. Ziemann spells it out easily and succinctly in this book. It is not merely mentioned, it is taught. This one point of instruction alone is worth the cost of the book.
As long as the bassist has a basic foundation in reading music and jazz (I would recommend this to an intermediate to advanced-level player), s/he will be able to learn in his or her own way. Ziemann outlines the best course of study in a modern format for different types of learners and players. Backing tracks are provided, and the player is encouraged to learn at his or her own pace. This is a book from which a player can learn from, then continue to refer to, as s/he becomes a more fluent soloist.