Solution: The Case of the Many Blanks
Answer: JUDICIAL

Written by Jonathan and Celestine

This puzzle presents a lot of blanks, and not much to work on. However, there are 2 key pieces of information in each minipuzzle that should help identify each series, the first is the punctuation, spacing and numbers present in the titles, and the second is the number of lines in each series, which have been given explicitly. Once a couple of the series have been identified and/or the puzzle title should clue that we are looking specifically for detective/mystery book series, which should help narrow down the search space further. The full titles are:

James Patterson’s Women's Murder Club series
1st to Die
2nd Chance
3rd Degree
4th of July
The 5th Horseman
The 6th Target
7th Heaven
The 8th Confession
The 9th Judgment
10th anniversary
11th Hour
12th of Never
… 12 more …
Minipuzzle answer is IRATE GRIEVER

Sue Grafton’s Alphabet series
"A" Is for Alibi
"B" Is for Burglar
"C" Is for Corpse
"D" Is for Deadbeat
"E" Is for Evidence
"F" Is for Fugitive
"G" Is for Gumshoe
"H" Is for Homicide
"I" Is for Innocent
… 16 more …
Minipuzzle answer is BENT LIGHT

Alexander McCall Smith’s The No. 1 Ladies' Detective Agency series
The No. 1 Ladies' Detective Agency
Tears of the Giraffe
Morality for Beautiful Girls
The Kalahari Typing School for Men
The Full Cupboard of Life
… 19 more …
Minipuzzle answer is LYING BIRD

Encyclopedia Brown, Boy Detective
Encyclopedia Brown and the Case of the Secret Pitch
Encyclopedia Brown Finds the Clues
Encyclopedia Brown Gets His Man
Encyclopedia Brown Solves Them All
Encyclopedia Brown Keeps the Peace
Encyclopedia Brown Saves the Day
Encyclopedia Brown Tracks Them Down
Encyclopedia Brown Shows the Way
… 20 more …
Minipuzzle answer is MENACING WIDOW

Lilian Jackson Braun’s The Cat Who… series
The Cat Who Could Read Backwards
The Cat Who Ate Danish Modern
The Cat Who Turned On And Off
The Cat Who Saw Red
The Cat Who Played Brahms
The Cat Who Played Post Office
The Cat Who Knew Shakespeare
The Cat Who Sniffed Glue
… 21 more …
Minipuzzle answer is FAKE LADY

The 5 minipuzzle answers are:
BENT LIGHT
FAKE LADY
IRATE GRIEVER
LYING BIRD
MENACING WIDOW

We can now find a 6th book series, with book titles that takes the form “The Case of the xx xx”. This series is the Perry Mason detective book series, and each minipuzzle answer is a synonym of one of his books:
The Case of the Dangerous Dowager
The Case of the Crooked Candle
The Case of the Perjured Parrot
The Case of the Angry Mourner
The Case of the Spurious Spinster
We can index into these titles by the indices given to get the final answer: JUDICIAL, an apt description of this series!


Author's Notes

The inspiration for this puzzle were the many other hunt puzzles using Agatha Christie mystery series. I found it strange that the Perry Mason series has not featured as all in any hunt puzzle I have tried, especially since it is supposedly the third best selling book series.

My original idea was minipuzzles that were other popular book series with words repeated in all the books removed. Celestine suggested limiting it to only mystery/detective series, and using the punctuation in titles and number of books to help clue the series.

The Sue Grafton series not having a word for X and not having a Z book prevented me from using it in the I know my ABCs puzzle, so I was glad to be able to use it here.