ENT: Strategem

Stratagem opens with a scruffy looking Captain Archer in a shuttle with an equally scruffy Xindi Primate, Degra. It soon becomes apparent that Archer is not actually fleeing a Xindi prison camp, but has set up an elaborate ruse to get information out of Degra. While they do not get quite the information they wanted, they do get one step closer to their goals.

ST Mirror Universe: The Sorrows of Empire

Combining short stories from previous Mirror Universe collections and weaving them into a cohesive whole, The book by David Mack looks at the question of "Our Universe's crew exposed the logical Mirror Universe Spock to dangerous concepts; what did he do with them?". Starting with Spock's inevitable assassination of Captain Kirk and ending with slightly after his death, this is a must read for anyone who thinks the Mirror Universe is much cooler.

ENT: Chosen Realm, Proving Ground

In Chosen Realm, the Enterrpise meets a ship full of aliens who worship the Xindi spheres. While helping them repair their ship at first seems a way to get much needed information about the spheres, it drags the Enterprise into an internecine war. Nice use of "Let's fake an execution with the transporter".
Proving Ground has some familiar characters joining the Enterprise in Xindi space. General Shran has taken advantage of the Andorian's superior warp capability to catch up to the Enterprise, ostensibly to offer assistance. In the end, it is of course revealed that the Andorians had an ulterior motive.