Hit and miss, with more solid books than bad books. As could be expected, there's a few gems, a few lemons and a few oddballs. The first dozen or so Dark Age books, with the exception of books 1 and 2, are often described as low points in the entire series.
Naturally, we're talking gaming fiction here, not grand literature.
I'm not aware of a review of the entire novel line. But here's
my review thread of the German-only BattleTech novelsYou might want to check out the
List of BattleTech novels on the Sarna.net BattleTechWiki.
Many additional novels and novellas have been published electronically via BattleCorps, and some of them are excellent.