I remember the original Haynes manuals from the sixties, having used several for working on Austin-Healeys and MGs. I remember them as having a lot of character, and reading them was almost like a conversation with a crusty old mechanic. Those old books seemed to share my love for these absurdly fragile and troublesome cars. This new book for the Miata shares little beyond the "Haynes" logo with with its legacy. Sadly, this new Haynes manual has a style more along the lines of Chilton's or other "fix your jalopy" guides. That is to say, no style at all. And no love.
What is more, the book suffers from assembly-line construction, with boiler-plate sections on tires, batteries, body care, etc., that are way too generic to be of any value to a Miata owner/lover. For example, the battery section is for a lead-acid battery, never mind the Miata has a "gel-cell" type. Want to set the timing on your Miata?... you won't find sufficient information in the Haynes guide to do the job.
The advantage to the Haynes guide is, it's cheap compared to the factory service manual. But, in this writer's humble opinion, it's not worth what it cost.