17a usual 3 letter word for favourite... can't quite see the parse but extra is O ... leaving east cast ...E must come out of some word to give the answer?
26a again can't parse but it's a tent T is extra
32a one who provides is defn ...extra is S from sentry ...you need a 4 letter word for entry/method of entry into house with N inside (either side of No teN)
25d strong drink is the defn think Obama with an extra R ... N is extra
28d former king is defn ...E in hopes is extra ...then it's an anagram of what's left with Y (terminal letter of regency)
32d trace is the defn ...T in stay is extra...say = usual 2 letter abbrev
in the shaded cells reading NW to SE you should have 1,2,2,1,1,2
the last letter of 28a( in shaded box) is the last letter of a novel by author 1 (his most famous)
The other letters in the shaded cells are also cryptic indications of a book title by the other 5 authors ... in most cases their most famous book....
2nd author 6 letters