The Path of Freedom (Vimuttimagga), by the arahant Upatissa.
This one's a classic, both literally and figuratively.
Areas of special interest to hardcore meditators include but definitely are not limited to:
> Introduction to concentration: Chapters IV, VII, and VIII (all sections)
> Especially PDF page 219 *(printed page 156) which describes a great Mindfulness of Breathing technique
> The siddhis, for those who have a skilled teacher: Chapter IX
> Introduction to Wisdom/Insight: Chapter X
> Insight Methods and Maps: Chapter XII
* The Table of Contents starts at the 52nd page of this PDF. The page numbers of the printed book, which are listed in the ToC, are 63 pages off -- ToC page 1 starts on the 64th page of the file.
Like many classics, this book is loaded with dogma -- but
the meditation instruction is first-class.
P.S. since MCTB recommends checking out the Vimuttimagga, could one of the wiki editors add a link there?