The basic idea of this story, like so many of others Harris wrote, is; 'take an interesting historical period, throw in some Noir, mix, add fascinating and beautiful femme fatales to flavour'.
It's a recipe that usually works, but, just like your basic meat-and-potatoes, it's not something you'd serve for a gourmet meal unless you're a really genuinely good chef. Harris is rather more my mother throwing together a nice but not terribly inspiring dinner than the three-star restaurant serving a steak, but, hey, I don't go out to restaurants every day of my life, and my literary cuisine can use an occasional homemade plain meal.
The basic story focuses on the WWII decryption of the Germans' Enigma code; a feat which both helped win the war - perhaps singlehandedly won it - and was the root of yours truly's review sitting out here today, and you being profoundly bored by it. The time and place where electronic computing first came into being, though Harris doesn't put much emphasis on that. The protagonist is Tom Jericho, a brilliant mathematician and cryptanalyst with large amounts of hormones. He falls in love with a seemingly vapid, but admittedly gorgeous, blonde named Claire, has a nervous breakdown, breaks the Germans' code, goes away, comes back, and gets into trouble. All in about four chapters. Then things get really tangled.
Part of my problem with this book was that I'd just recently read through Collins's Woman in White, and reading Enigma rather reminded me of that mystery classic. There you had Laudanum, here you have Germans and U-Boats. Much of the rest of the plot seems like a reflection of that other book, told more succinctly, and with less appeal to diaries.
So my problems with The Woman in White, which I actually found an excellent book by and large, were neatly reflected here, as well. Of course, whereas the former was written by a well-known Victorian misogynist, Mr. Harris has no such excuse. I hope he realizes just how tired the average female reader grows of reading about the intelligent but plain woman who busily aids in the investigation being shuffled off as a potential love interest for the sake of the beautiful and feminine damsel in distress. Honestly, I get quite bored. One would think a mathematician, a person to whom his profession is everything, would be inclined to seek out a mate he could actually talk to, rather than one simply to look at. I mean, if he really needs perfect beauty to admire, he could buy a painting, right?
But no, we must follow up with the cliche. After all, if we put too much pepper in the potatoes, some bland and banal palate might not appreciate it.
And no adding any sort of odd sauce to the dish, either. The bleak, noir world of Bletchley Park - which happened to be criticized by people who were there - is the perfect grim and grimy setting for a crime; the character is a sort of traumatized and disillusioned noir detective, maths style, dismissed and later re-evoked for his brilliance. There's a scene of him losing his badge (for the Nth+1 time). The foolish supervisor is there, the obstructing bureaucrat is there, the loyal but uninspiring coworkers are there...
Mind you, the book as a concoction is not at all bad, like my mother's cooking isn't - at least, it's wonderful cooking anywhere within hearing of my mother - and it has its merits. For one, the math and cryptoanalysis is well-researched and explained. The fellow is no Stephenson, I suppose, but so far as I could tell, being a mathematician only by marital proxy rather than by inclination, he wasn't Dan Browning the whole affair.
Also, the book, although it drags at times, is eminently edible - I mean, readable - and digestible by pretty much anyone. I can't really point to a person or demographics and say 'no, don't read this'. It may not enthrall or impress you, but, really, there's very little chance that you'll throw it into the garbage bin after taking a single bite.