what is the blue indicator below the book?

Tim Murray

It appears to be some kind of progress indicator but one book shows a pretty much solid line, the other book it has gaps in the blue line.

JT (alabama24)

Tim Murray said:

It appears to be some kind of progress indicator but one book shows a pretty much solid line, the other book it has gaps in the blue line.

It is a progress indicator… If there are gaps, it is likely that you skipped around (or at least that Logos has interpreted it that way).