Can a Series of Letters Make for a Good Detective Novel?

THE DOCUMENTS IN THE CASE.
By Dorothy L. Sayers (1893-1957) and Robert Eustace (1854-1943).
Gollancz/Brewer & Warren.
1930/1931. 304 pages.

Martin Edwards's choice for an unjustly forgotten book is this one from Dorothy Sayers: 

There are a number of intriguing themes in the book, but what has always fascinated me is that this is an epistolary novel. The story told through letters by various hands appears to be relatively commonplace but, bit by bit, a complex set of relationships is presented.

See also: 

A book of letters by one whose own letters are full of interest in their own right, with the assistance of a scientist whose collaborations with L. T. Meade are acknowledged classics. The epistolary form allows D.L.S. to present the same characters from different perspectives, and so lend them a depth lacking from other works. — Nick Fuller

. . . as well as: 

Sayers' citing of L. T. Meade as the founder of scientific detection has been much quoted since, by Ellery Queen and others. Sayers was the first to identify Meade as the founder of scientific detection. Sayers collaborated with Meade's partner Robert Eustace on 'The Documents in the Case' (1930), and she is the sole source of the information that Meade was responsible for the writing and Eustace for the scientific ideas in Meade and Eustace's stories . . . One problem with [this book]: Sayers deliberately wrote [it] so that the identity of the killer would be obvious early on. She asserted that it was much more interesting to try to figure out how the crime was committed, than who done it. — Mike Grost

A lengthy collection of other opinions about DOCUMENTS is here.

Following find a full contemporary review (William C. Weber, THE SATURDAY REVIEW, July 18, 1931; scroll to page 981, lower left):

Dorothy Savers dips deep into laboratory lore for the mechanism of her latest murder yarn, "The Documents in the Case", written in collaboration with Robert Eustace, who, one gathers, invented the method by which an unwanted husband was put out of the way. In any other hands but Miss Sayers's it would be too scientific, but that expert writer makes it an interesting tale, in spite of the damnable stylistic device of a series of letters which usually drives this reader to distraction.

D.L.S.'s own opinion:

In my heart, I know I have made a failure of it . . . I wish I could have done better with the brilliant plot.

 Category: Detective fiction