Letters From Home is an unabashed puzzlefest. There's almost no plot whatsoever. That's absolutely fine by me - this game just wants to be a vehicle for word puzzles, and thankfully they're mostly good puzzles.
There's a cryptic crossword at the end of the game, but the whole game is cryptic, really. You need to have a talent for puns and lateral thinking for this one. I'm quite good at those so I enjoyed myself immensely, but this isn't as consistent and fair in its wordplay as Ad Verbum (for example). Then again, neither is almost every cryptic crossword I've tried.
Most solutions are clued well enough in-game (outside of the Hints menu), but you occasionally run into a bit of under-implementation, and a few puzzles are very obscure - I could have played for a million years without hints and not figured out where the N was hiding. Also, I don't think the time limit adds anything to the game, except for stress when you're trying to find an NPC who walks around randomly. (Thankfully, there's no punishment for exceeding the limit apart from the ending saying "*** You have lost ***".)
The writing is fun considering there's not much of a story. There's a surprisingly good sense of place, and of the PC's relationship to the priory. The jokes are daft too. I wish the NPCs were a little more detailed, but I like the incidental ways they interact with each other.
I'm fond enough of Letters From Home to give it 4 stars, but 3.5 stars (its average at the time of writing) is probably about right. You'll get a lot of the puzzles and feel pretty smart, but just be prepared for the really obscure bits of wordplay.