The anime pretty much follows the book until the ending, which cuts out the part with the Linsdays.
Yes Marnie and Anna say they love each other. So that whole "queer baiting" thing is in the book too if you want to call it that. It's pretty much that Marnie was forced to marry Edward and then had kids.
Overall the book is pretty good if you like slice of life type books were not much happens and there's no super magic stuff going on.
I felt the part with the Lindsays was drawn out a bit much. They are mostly there to get you hyped for the big reveal of who Marnie was.