Thanks for the quotation, but "Raptor of Spain" is defunct? Are you sure of that?
Return to the topic, my favorites are "Isaac's Empire", "Raptor of Spain", "The Song of Roland", "Tuscan Sons", "The Prince of Peace".
What's make a good medieval timeline?
1) Knowing the facts and avoiding false easy PoDs. Such things as a Muslim Europe after a frankish defeat at Poitiers are too easy and relying only on a "assumed knowledge".
A TL writer must interest himself to the actual facts and not standing on the surface (dates, maps, etc).
2) Understanding the mental structures.
Granted, the medieval men and women had the same needs, the same organism than us. But Middle-Age was so different regarding institutions (political or cultural), juridic separations of social classes, that is a need to at least be aware of that.
Critically regarding religion and intolerence.
3) Knowing his geography and adapting it.
In MA, geographical features were more important than today. Forest, marshs, basin are each one a potential border.
In the same time, remembering that these borders weren't clear most of time, and more based on grey zones that limes.
4) A medieval TL isn't a Crusader Kings game.
A good writer must be interested on other things than nobles, warfare, politics and economics. How changes (critically in a period like MA where radical changes can happen quickly) are modifiying the lifes' conditions of the masses : urbanism, tools, favourite colors (don't laugh, the choice of Blue as the favorite color of the western world instead of Red is very interesting)...