I read and analyze a text primarily for personal pleasure but also on the assumption that my audience either has already read it or at least does not mind being told details of an as yet unfamiliar text. Otherwise, of course, SPOILER ALERT!
There is always a surprise. In SM Stirling's Conquistador, characters pass not between our timeline and one alternative timeline but between two alternative timelines. Consequently, my next post, probably not till next month, will address the differences between three timelines, our one and their two. Dig it.