booking_along 's review for:

A lost letter from Mal by Leigh Bardugo
2.0
medium-paced
Plot or Character Driven: Character
Strong character development: No
Loveable characters: No
Diverse cast of characters: No
Flaws of characters a main focus: Yes

mhm 
was that necessary? no.
is it important to read for or on the series? absolutely not. 
did it add anything at all? not really.