For Book Lovers Only: The word Book can come at the End of the word that the letters spell out to give us a new concept. The circles make a nice Bookend for the letters in-between.
17-Across. "Almost!": NOT QUITE. Notebook.
22-Across. Bargain hunter's event: RUMMAGE SALE. Rule Book.
  38-Across. Rush hour woe: COMMUTER TRAFFIC.  Comic Book.  Odd man out, since there are 3 letters at the
  beginning, and only 2 at the end of the answer.
49-Across. Lingers: HANGS AROUND. Handbook.
And the Unifier:
61-Across. Items found on library shelves, and what are literally found in each set of circled letters: BOOKENDS.
Here's the Grid:
Across:
  1. Prickly desert plants: CACTI.
  6. Oolong and rooibos: TEAs.  Who knew there were so many types of teas.  Rooibos is a red tea and is considered an herbal tea because it is
  caffeine-free.
  10. "The Problem With __": documentary about Indian stereotypes on "The
  Simpsons": APU.
  13. In order to: SO THAT.  In order to complete this puzzle
  ...  So that I can complete this puzzle ...
14. Puts on edge: UNNERVES.
  16. Springs for dinner: TREATS.
18. Distant: AFAR.
  19. "Gorillas in the Mist" animal: APE.  Gorillas in the Mist is a 1988 film about Diann Fossey (Jan. 16, 1932 ~ Dec. 26, 1985) and her work in Rwanda with mountain
  gorillas.  Sadly, Fossey was murder in her research cabin in Rwanda.
  21. Answering to: UNDER.  Think chain of command.
26. Dairy farm animal: COW.
  27. Majestic homes: PALACES.  Do you know the difference between a Palace and a Castle?
  32. As good as it gets: IDEAL.
  36. News inits.: UPI.  United Press International.
  37. __ Beds National Monument: LAVA.  I was not familiar
  with Lava Beds National Monument.  It looks beautiful and you can explore caves there.
  42. Actress Falco: EDIE.  Edie Falco (née Edith Falco; b.
  July 5, 1963) is probably best known for her role as Carmela Soprano on the
  television series The Sopranos.
43. "I'm __ ears!": ALL.
  44. Iona College athletes: GAELS.  Iona College is a private
  Catholic college in New Rochelle, New York.  The mascot looks a bit like a creepy Abe Lincoln.
  45. Major plot twist in "The Wizard of Oz"?: TORNADO.  Cute
  clue!
47. Happy __ clam: AS A.
55. Permit: ALLOW.
  59. Syst. with hand gestures: ASL.  As in American Sign Language.
60. Away from shore: ASEA.
64. Ludicrous: ABSURD.
  66. Response to someone saying 65-Down, perhaps: BUNDLE UP.
   //  And 65-Down: "It's c-c-cold": BRR!!!
  67. Hairstyle that may be maintained by a professional
  "loctician": DREADS.
68. Had a bite: ATE.
  69. Relay race segments: LEGS.
  70. "R u for real?": SRSLY.  Text speak for Seriously.
Down:
  1. Resort island in the Ionian Sea: CORFU.
2. First-stringers: A-TEAM.
  3. __ City: Baltimore's nickname: CHARM.  Is this an ironic nickname for Baltimore?
4. Skin art, for short: TAT.
5. "We're on!": IT'S A GO.
6. Melodies: TUNES.
  7. Roxy Music co-founder Brian: ENO.  Brian Eno (né Brian
  Peter George Eno; b. May 15, 1948) makes frequent guest appearances in the
  crossword puzzles.
  8. "__-Man and the Wasp": ANT.
  9. Title with a "II," maybe: SEQUEL.  Do you think that there
  will be a sequel to 8-Down?
10. Passionate: AVID.
  11. Transportation Secretary Buttigieg: PETE.  Pete Buttigieg
  (né Peter Paul Montgomery Buttigieg; b. Jan. 19, 1982) was the 32nd Mayor of
  South Bend, Indiana before he became the 19ht United States Secretary of
  Transportation.
12. Icon tapper: USER.
  13. Polaris or Betelgeuse: STAR.
  15. Part of RBI: RUN.  As in the baseball abbreviation
  for Runs Batted In.
20. Chapel bench: PEW.
  23. Rights advocacy org.: ACLU.  As in the American Civil Liberties Union.  The ACLU has been around for over 100 years.
  24. Datebook entry: Abbr.: APPT.
  25. Wild animal's home: LAIR.
  28. Communications code word for "A": ALFA. 
29. Casual eatery: CAFÉ.
  30. Really, really bad: EVIL.
  31. Biological pouches: SACS.
  32. "Rhyme Pays" rapper: ICE-T.  Ice-T (né Tracy Lauren
  Marrow; b. Feb. 16, 1958) is known as Detective Tutuola on one of the Law & Order series.
  33. Knucklehead: DODO.  CSO to our dear friend Dodo, who
  certainly wasn't a knucklehead.
  34. Dubai dignitary: EMIR.  This is becoming a crossword
  staple.
35. "Right on!": AMEN.
  36. http follower: URL.  The Uniform Resource Locator appears with some frequency in the puzzles.
  39. "And here it is!": TA DA!
  40. Musk of SpaceX: ELON.  Elon Musk (né Elon Reev Musk; b.
  June 28, 1971) has been the news a lot recently.  Enough said.
  41. Seaweed gelatin: AGAR.  Agar makes the base for growing
  bacteria in the laboratory.
  46. "Can't be helped": AH, WELL!
  47. Pack animal: ASS.  This is becoming a crossword staple.
48. Light lunches: SALADS.
  50. "Oh my gosh!" reactions: GASPS.
  51. Fertile desert spots: OASES.
52. Garden-variety: USUAL.
53. Square: NERDY.
  54. Both parents, in some families: DADS.
  55. "Mamma Mia!" pop group: ABBA.
56. Boor: LOUT.
57. Only: LONE.
58. Approved, briefly: OK'D.
  62. Word before a maiden name: NÉE.  Today's French lesson.
63. Really grooved on: DUG.
Now it's time to get back to my reading.
  חתולה
 
