Today's theme goes top to toe bringing together two body parts - or a BODYDOUBLE - that together add up to something else entirely, giving us RIBJOINT, MOUTHORGAN (which isn't gross, but kinda seems it somehow), KNUCKLEHEAD (my favorite), and BACKLASH (which gets in by a hair - if the eyelash counts as a body part). Once I finished typing that sentence, I thought I should try to find out if eyelashes *are* considered to be body parts. I didn't spend enough time on it to find a definitive answer, but I did learn some very interesting things about eyelashes. Kneeto!
Topics-wise, one could say that the constructor and I see eye to eye. I always enjoy a library-themed clue (1A: Library catalog listing after 'author'" (TITLE)), and Author ISAAC Asimov is a old favorite. I'm also a fan of the REUSE philosophy. Waist not, want not!
Other clues that were music to my ears were "Lightly touched, as with a handkerchief" (DABBED), "Apt letters missing from '_tea_th_'" (SLY), and "Flub" for ERR. On the other hand, when filling my own lunchbox (so to speak), I prefer a PBANDc to a PBANDJ. J has never been my cup of tea. Other ASSETS include GUSHES, PLACID, and PLATEAU.
I didn't need to use much elbow grease to complete this puzzle, but I did have to take a moment at 23D: when I read the "dos" in "Half of dos" as in 'dos and don'ts'. I already had the final O so I spent a little minute trying to get some form of 'no' in there instead of the correct answer UNO. The only other real hiccough was a virtual armload of abbreviations like ATL, MGRS, ISO, SPF, and UTIL. Butt, overall, I'd say the puzzle had very good bones and was a real GAS.