While I haven't specifically done Audiobook editing, I have edited VO and Narration (close cousins to Audiobook). And the closest comparison I can draw is dialogue editorial.
here's a post which may help:
Looking for some help on dialogue editing?
First, I respectfully disagree with George on the decision to go away from a NLE like ProTools. I can't even fathom how painful dialogue (and dialogue-related) editorial would be if I couldn't chop, splice, arrange, and nudge around my material in a sort of 'sandbox' of tracks with flexible regions of sound. Especially because many times we're working on sub-frame scales to do triage work and stealing phonetic pieces here and a consonant or vowel there to make correction, chopping out a pop here or smoother over the lip smack there.
When I cut dialogue, I prefer to take the 3-pass approach noted above in the link. Above all else it helps me stay on schedule and devote equal amounts of time to the dialogue - and it prevents the psychological 'writers block' from occurring where the editing feels like its' never ending - making it through to the end once provides a sigh of relief, and comfort that you can easily do it again on the next pass and it eventually won't feel daunting as though you're never going to reach it. During the first two passes, I have a rule which may help you. When I roll up upon a challenging place which needs work to massage it into place, I'll allow myself 2 minutes to fix it - if I can't make it happen in those 2 minutes, I'll drop a marker and move on, wherein I'll take another stab at it on the next pass. Funny enough too, coming back to it later with fresh ears and clear mind can make it really easy to solve. I've personally had some situations where I spent a lot of time trying to make a scene work, gave up and moved on. I can back the following week during my next pass, and banged out the scene in a matter of minutes.
I do agree with George about shortcuts though, learn your shortcuts. The essentials for dialogue in my opinion are hotkeys for trimming, duplicating, snapping regions (front and tail snapping), selections, nudging, nudge value changes - amongst some others.
Aside from that, a lot of it just takes repetitive practice. My first dialogue edits for 90 minute material probably took me six weeks too. But through a lot of repetition and developing a workflow which works for me, I've got it down to banging out a solid, detailed dialogue edit of equivalent duration in about 2-3 weeks tops (and on some brutally-fast occasions, 1-2 weeks - but I don't recommend that, and in those cases usually 'pass 2' from that link gets sacrificed for all but the most egregious problems).
Frequent breaks help too. A 5 min break every hour or two is what works for me. Sand up, stretch, make any phone calls you need to make, go grab the mail, go for a walk, a bathroom break - just something to clear your head for a few moments and ground yourself again. For me this is especially critical when undergoing 'pass 2' because of how micro-detailed and grueling of a process it can feel.
With time and persistence, you will get faster and more proficient at it than you probably feel right now. Unfortunately dialogue/voice editorial is one of those skills which can't be rushed but in due time, you will see results and reap the rewards of 'paying your dues' from within the trenches of repetition.