Yes, @Artemisia is correct 
you can always share book reviews in the current book club session! If you have trouble finding it, you can also post a review in the Recommendations category and we can move it for you if we need to.
To find the current book review post, it’s always listed at the top of this post → 
Spells8 Book Club! - Introduction and FAQ
Nope! There’s not a time limit at all. The review session that opens is just to separate the books that were read for January from the ones read in February. You are welcome to post your review in the current book club session whenever you’d like! When the review post opens, all early reviews posted get moved to the review post to make it easy for people to find them.
I hope that answers your question! Please let me know if you still need help with it. I admit it can be a bit confusing 