When it comes to official histories, Moberly's coverage of some of the "forgotten fronts" stand out as some of the best, and Operations in Persia is no different. Moberly is more commonly associated with his Campaign in Mesopotamia (1923-1927, 4 vols). However the tangential operations in Persia were linked in many different ways to the campaign then being waged in Mesopotamia. This detailed volume is the most detailed accounting published on the campaign by far, surpassing those rare first hand accounts (see Dunsterville or Donohoe's accounting for a first-hand view of the operations). Originally printed in a limited run of 500 copies in 1929, most of which marked either secret or confidential, many of the originals were destroyed, so coming across an original would be quite the find, but this is the more commonly accessible copy printed in 1987.
Moberly does a great job of covering the disparate facets of the operations in Persia, since for the majority of the war, they were directed from various quarters, but under the overarching cognizance of London and India. Great details on Sir Percy Sykes' South Persia Rifles, Dunsterville's move towards the Causcasus, and some very good detais on the campaign in Eastern Persia under Dyer and Malleson.
Moberly also has good source documents covering the German's attempt to raise the banner of jihad in Persia, or at least at best rally the tribes to agitate against the English and the very weak governments that governed somewhat ineffectively from Tehran. His coverage of Wassmuss and Niedermayer's (et al) exploits is as good as it gets, albeit probably not as engaging a read as it has been recounted by Hopkirk.
Not exactly bed-time reading due to the very detailed coverage of the campaign, but nonetheless a great recounting of a forgotten aspect of WWI. ( )