Unusually, I think, the title virtually gives away the theme. Certainly I wasn’t at all surprised when the theme revealed itself.
Twelve of the clues lead to an extra letter which spell two “related” names. A further five clues (without definition) lead to a thematic group. Further, the top and bottom rows of the grid lead to two titles. And, finally, Ten cells contain the name of the author in an “appropriate” shape.
I did my initial scan through the clues looking for likely suspects that had no definition. The first one I identified was 23d (TIMMY) thus confirming my suspicions that we were looking for The Famous Five (Julian, Dick, Anne and Georgina [George] – and their dog Timmy) by Enid Blyton.
The two related names are (Aunt) FANNY and (Uncle) QUENTIN though I just cannot see where the second N in FANNY comes from 🙁
Finally, ENID BLYTON is hidden in the grid in the shape of a 5 (cells: f9, g9, h8, h7, g6, f6, f5, f4, g4, h4)
There are a couple of answers which I don’t really understand (10a & 21d), noted in the lists below, and I have a quibble with 11d.
All-in-all, a nice easy puzzle after the last two stinkers I had to blog. 😉
Footnote: Thanks to Colin and HolyGhost for their comments. I have changed the explanation of 4d and I’ve changed the incorrect Wikipedia link.
Thematics:
Across:
| No. | Extra | Entry | Definition | Wordplay |
| 10 | ANODES | Conductors | I just can’t see how this one works 🙁 Clue: Innocent party can finally put out last of bus conductors. | |
| 12 | ENGOBE | Slip | EN (nurse)+GO (to fare)+BE (to live) | |
| 13 | See above | |||
| 14 | THERETO | In addition | [tak]E+TO+HEART (minus A(nswer)) (anag: reworking) | |
| 15 | F | NATAL | About (US) can (buttocks) | N(ote)+FATAL (critical) |
| 16 | A | SINGLY | Alone | SING (celebrate)+LAY (bet) |
| 17 | MILICE | Wartime French collaborators | MIL(itary)+ICE (kill) | |
| 20 | N | ORWELL | Author (George Orwell) | NO (drama)+R(uns)+WELL (easily) |
| 25 | ODIOUS | Offensive | O(ld) +O(ld)+I (one) inside SUD (south in French) (rev: repelled) | |
| 27 | SWEIRT | Lazy (Scottish: For Angus) | W(ife) inside TRIES (proves) (rev: over) | |
| 28 | DISPLE | Chastise | [a]CI[d] removed from DISCIPLE (student) | |
| 29 | DORMS | Where boarders might sleep | DO (clean)+RMS (rooms) | |
| 31 | ENTOTIC | Souse’s (ear’s) inner workings | EN (space)+TO (for)+TIC (response) | |
| 33 | Y | ITEM | Make a note of | [fru]ITY EM[ails] |
| 34 | REHEAT | Fuel injector | RE ((Royal) Engineers)+[c]HEAT (chisel) (minus C(old)) | |
| 35 | KEYNES | Economist (Maynard Keynes) |
KEY (crucial)+SEN (without) (rev: backing) |
Down:
| No. | Extra | Entry | Definition | Wordplay |
| 1 | Q | STETSONS | They’re worn by cowboys | STET (reinstate)+SONS( products) |
| 2 | URGE | Drive | QU(een)+R[a]GE (A(cting) out) | |
| 3 | See above | |||
| 4 | U | GABELLER | Tax collector | GAB (talk)+L(atin) inside EULER (mathematician) |
| 5 | E | ENTOMB | Bury | TEEN MOB (anag: riled) |
| 6 | ROAN | (double definition) | (double definition) | |
| 7 | N | TENTIGO | Lewdness | TENT (camp)+INGO (reveal (Scottish)) |
| 8 | PEEL | Shovel | PEE (stale:urine)+L[and] | |
| 9 | ON HIRE | To let | [f]INE H[a]R[l]O[t] (minus FLAT) (anag: upset) | |
| 11 | DAALS | Pulse (surely this should be pulses!) |
D(ead)+[b]AAL (false god) (not B(orn)) | |
| 18 | T | INDITERS | (Former) dictators | I(nstitute)+STRIDENT (anag: overthrown) |
| 19 | EXSECTED | Cut out | EX (without)+SEC(ond)+TED (spread) | |
| 21 | WHERE’ER | In whatever place | I can see W(eak)+HER but nothing else 🙁 Clue: Weak, She drinks endlessly in whatever place. | |
| 22 | See above | |||
| 23 | See above | |||
| 24 | I | STEVEN | (local) Voice | SIT (be comfortable with)+EVEN (calm) |
| 26 | ISOHEL | Contour | O[outgrowt]H (hollow) inside LIES (anag: unevenly) | |
| 29 | See above | |||
| 30 | SUNI | Antelope | SUN (nearby star)+I[njure] | |
| 32 | N | TELA | Tissue | ANTLE[r] (nearly) (anag: damaged) |

I didn’t do this puzzle so may be missing part of the theme but isn’t the mathematician EULER rather than EULLER?
I too failed to find the other N in FANNY. (When I blogged Samuel’s previous puzzle, 1176, I remarked that I couldn’t find the final A in ATALAYA – but no-one bothered to respond to that.)
10a: ANODYNE (=innocent) – (part)Y (ca)N + (bu)S.
21d: I finally decided that the remaining EER is (b)EER(s), i.e. “drinks endlessly” means both ends missing.
And Colin B. is right: the mathematician at 3d is EULER; the extra L comes from L(atin).
And at 11d (which I missed because Ken just used “!”, not an emoticon), Ch. has “pulse” as noun singular or plural, so I guess the clue’s OK.
I though I had the second N in 31A, but on attempting to explain it again I have forgotten where it came from (or I made it up!)
I had (b)EER(s) like HolyGhost in 21D but thought it a weak(!) clue.
Thanks HG for the explanation of 10A which utterly defeated me.
A fun puzzle though, and the shape of the five for Enid Blyton was a nice conceit.
The title was probably too much of a give-away though. Those of us who have read (some of) the books to both children and grandchildren know far too much about the characters in that series!