I can verify that you can download updates for one year after date of purchase. I have two of the updates.
I don't know if I can give it a glowing recommendation for content. What is there is mostly correct but there is so much to cover in MSFS that any guide would need many more pages to do it justice. My strong preference would be for a physical, printed and bound copy like those things they used to make called books. That way I could quickly flip to the page marked with a post-it note while still keeping one hand on the yoke. But IMHO it is the best guide to MSFS available.