Does it count if they're not in the same medium as the 'later' works? Because the Myst prequel novels are superb.
The Book of Atrus is a prequel to the games, and is very good. The Book of Ti'Ana is a prequel to the prequel, and is even better. There's a third book, but it's not a prequel to anything and is the weakest of the three (still good though).
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"I'm Commander Shepard, and you're standing in the biggest library in Citadel Space. Look me up."