Times without number

This easily readable tale is set in quite a well-made alternative world, has an active and well-paced plot and a good range of characters, and is competently written by the standards of 1960s sf. It explores the theory of time travel interestingly and described Larry Niven's law of time travel before Larry Niven did.However, it feels like a minor book, and when I decided to read it I had no memory of it, although my records tell me I've read it twice in the past. It's not a book that sticks in the memory. Why is this?1. Although there's a range of diverse characters, none of them make much impression on the reader. I've spent the whole book in the company of the hero, Don Miguel Navarro, loyal subject of the Spanish Emperor, but his personality remains elusive: I don't feel I know him. If I compare this to Randall Garrett's [b:Lord Darcy 880461 Lord Darcy (Lord Darcy, #1-3) Randall Garrett https://i.gr-assets.com/images/S/compressed.photo.goodreads.com/books/1388708394l/880461.SY75.jpg 3103213] stories, which have a roughly similar 1960s writing style and a roughly similar kind of scenario, Garrett had the knack of quickly establishing the distinct personality of each character and then keeping it consistent; but Brunner lacked this knack. The personalities of his characters, although somewhat different, are neither clear nor consistent: they're blurred and seem to wander about a bit.2. The typical writing style of 1960s sf seems by now rather dated; the state of the art has advanced since then. This is not a deterrent if the story and the characters are good enough, but it's worth mentioning if the story or characters don't stand out. 3. Although I take some interest in it, sometimes time-travel theory gets too technical and I just want to read the story. It's a common hazard of sf that some authors tend to be fascinated by technical details that are less interesting to most readers.So, I quite liked this book, it was quite a worthy effort by the standards of the time, but in another five or ten years I'll probably have forgotten it again. It lacks the memorable characters and dramatic scenes that make a work of fiction stick in the memory.