You wouldn't want to be operated on by Dr. Gonzo in Hunter S. Thompson's "Fear and Loathing" here
Las Vegas
It follows Jiffy in the name of a car repair chain
Lube (Blue)
This letter is right by 221 in Sherlock Holmes' street address
B
Zeta is actually the 6th letter in the Greek alphabet; the last one is this
omega
To dig up, specifically the deceased
Exhume
"The Island of" this doctor by H.G. Wells concerns a man trying to turn animals into men
Dr Moreau
You could be a fire or army type in a colony if you're this
ant (tan)
When this letter follows 4, it means not qualified for military service due to medical reasons
F
It's not the 3.14th letter in the Greek alphabet--it's the 16th
Pi
The Screen Actors Guild gives an acting award named for this type of group on a TV series
Ensemble
Dr. Constantine is the coroner on the train who helps Poirot gather evidence in this novel
Murder on the Orient Express
A category or class of artistic endeavor, like science fiction
genre (green)
When it follows 3, this letter means having length, breadth & depth
D
It's not the 3.14th letter in the Greek alphabet--it's the 16th
Delta
Literally meaning "out of center", it means deviating in a peculiar or odd way
eccentric
Dr. Jeremy Stone tries to contain an out-of-this-world biological agent in this Michael Crichton novel
The Andromeda Strain
Anagram of an orangey yellow, it's a household task
Chore (ocher)
It follows 4 in the name of a youth organization that uses a clover symbol
H
This Greek letter, number eight, is represented here:

theta
Adjective for a speech given without advance preparation
extemporaneous
"All is for the best in this best of all possible worlds", claims Dr. Pangloss in this French novel
Candide
A purplish red anagrams to this person of great influence, especially in business
magnate (magenta)
It preceded 38 in the designation of the U.S. Army's Lightning fighter plane of World War II
P
This 9th letter of the Greek alphabet also means a jot or whit
iota
This river is described in Genesis as one of 4 flowing out of Eden
Euphrates