It is and they make it clear in rules with a box out saying if you've played Chrononauts then you pretty much know how to play but there are some differences that make it worthwhile scan reading rules first.
LOL - oh how the gamers mind works... This 'box' in the rules does talk about the differences but ends with "Anyway, do not assume you already know how to play, and please read these rules carefully. Thanks!" which is kinda the same as "you pretty much know how to play but it's worthwhile to scan read the rules first."
Thanks for the great review, Jeff - I'm glad you are enjoying the game!