A slightly more complete review now that I've actually finished reading it. One point I feel I should make at the start is that no, he didn't correct the second/third crusade mix up at the end in a brilliant time travel related conclusion, so I'm still annoyed with the lack of fact checking.
Actually, I'm a little unsure as to what the ending was, but we'll get to that in a minute. For now, the plot. World War II pilot Guy Goodlet finds himself whisked out of his soon to crash plane by time traveller, medieval bard, and most popular performing artist of all time Blondel, who is singing outside every castle in time and space (including the elephant and castle tube station) in an effort to find Richard the Lionheart. Goodlet agrees to help, principally because he falls hopelessly in love at first sight with Blondel's sister Isoude.
Various people aren't very happy about the great singer-songwriter's efforts. His time travelling investment banking managers, for one. The people who police time and space for another. And also the Antichrist, for some reason vaguely to do with the lease on the Earth having been negotiated by the aforesaid managers in a brief foray into the property market.
It's odd, to say the least. It's also very funny, in a wordy, observational sort of way. But then Tom Holt's books usually are. He has a knack for catching odd characters perfectly, and for providing exquisitely absurd similies.
It's just a pity really that it doesn't make a great deal of sense. Partly that's the fault of random time travelling plots, which rarely work. Partly, it's because things like Guy Goodlet's inexplicable ability to shoot off hats without ever hitting what he's aiming at look like they ought to have some hidden significance that never shows up. Partly, it's because the whole thing gets sorted out by a (literal) deus ex machina, which doesn't work even if you are jokingly pointing out that you're doing it at the same time. Mostly though, I got the feeling that Holt didn't have a clue how he was ending things, and as a result the apparent main character felt like a spectator.
All in all then, while it might be worth reading once (while on the blood pressure tablets if you happen to be a medievalist interested in the crusades) it's probably better to buy his his more recent, still hilarious but also coherent, novels instead.