Vintage Mystery Challenge 2019: Just the Fact's Ma'am...

I'll try again

Hosted here

Challenge Levels
   Constable: 6 books -- one from each category
   Detective Sergeant: 12 books -- two from each category
   Inspector: 18 books -- three from each category
   Inspired Amateur: 24 books -- four from each category
   Chief Inspector: 30 books -- five from each category
   Superintendent: 36 books -- six from each category
   Chief Superintendent: 42 books -- seven from each category
   Deputy Chief Constable: 48 books -- eight from each category
   Chief Constable: 54 books -- nine from each category
   Master Detective: 60 books -- all ten books from each category

Pre-1960

1960-1989 (inclusive)

My goal is Chief Inspector