UPDATE - 2/25@9:54AM: Last month in a Friday updates post I'd noted that Luthier Bruce Johnson revealed on the TalkBass Forum that Geddy had visited his shop this past fall to interview him for the book, specifically to discuss his knowledge of the history of Ampeg Scroll Basses. Johnson apparently also wrote a detailed blog post chronicling the visit, including several great photos, for the Packing House Creative website back in October as seen here (thanks RushFanForever). Geddy's co-author Daniel Richler accompanied Geddy on the visit and was mentioned in the post and can be seen in the photos:

... They are putting together a story about how the electric bass was developed, in the time period up to 1972. How it evolved, as different individuals and companies experimented with the design. And how that design affected how basses were played during the early days of rock music. As part of their research, Geddy and Daniel have been traveling around interviewing various people who know the background of the instruments of that time.

Geddy has a large collection of vintage electric basses of his own. Over the last few years, he's become interested the Ampeg Scroll Bass, an obscure model of electric bass which was made from 1966-1969. Those basses are my particular area of expertise. I've repaired and restored more than a hundred of them for customers over the past 20 years, and I have several of my own. I've done extensive research and writing about them. I also build and sell new improved versions of the Scroll Bass, as my main product line.

In his collection, Geddy now has 5 nice examples of these Ampeg Scroll Basses. As he acquired these basses, his long time instrument technician Skully has been in communication with me. I've helped them with technical problems and historical information.

So, they came to my shop mostly to talk about the old Ampegs, as research for the book. ...

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Without Rush to keep him occupied the past couple of years, Geddy Lee has instead been keeping himself busy by working on a bass guitar book project titled Geddy Lee's Big Beautiful Book of Bass. The book now has a tentative release date of November 13, 2018 and can already be pre-ordered from Amazon (thanks RushFanForever). It's currently listed at 360 pages, but the cover has yet to be revealed. Here are some more details via the Cooke Agency website:

Rock 'n' Roll Hall of Fame and RUSH bassist Geddy Lee's Geddy Lee's Big Beautiful Book of Bass is a gorgeous, fully illustrated love letter to rock 'n' roll's rumbly bottom end, complete with a guided tour of Lee's extensive vintage bass collection, personal anecdotes, observations and history, from one of the world's most revered and beloved masters of the instrument.

This lavishly illustrated book presents one facet of Lee's own personal journey. The bass guitar has been his passport, his vehicle, his fuel; this book will be his account of a life lived on the stage and a view of the world he's seen on the road.

With contributions from arts journalist Daniel Richler and Lee's trusted bass tech, John "Skully" McIntosh, with photography by Richard Sibbald, Geddy Lee's Big Beautiful Book of Bass will have something for every reader, from RUSH fans who want to know the inside story of Lee's relationship with the instrument that has given him so much in his life, to the most knowledgeable musicians and collectors. This will be the definitive book on the bass, from one of the most respected players in history.

Aside from the HarperDesign trade edition, there will be limited run of signed and numbered deluxe editions available as well. ...