Onto what might be my favourite book in the Jill series, it's this or pony trek...
Jill is convinced by Ann, after some prodding, to start a riding club and what follows is a 100% dream scenario of them getting together their members, tracking down an unused paddock and convincing its rather grumpy owner to let them use it for club rallies (shout out to my girl Mercy Dulbottle, MVP) and then spend a summer having fun, schooling and eventually setting up and having their own Gymhkhana.
There's a lot of returning characters here and also plenty of new ones, Clarissa and Cecilia are featured quite a bit, but they're pretty amusing in their own way so I don't mind it.
This book is just a dream honestly, a whole summer of riding your horse with your friends, with some decent equipment and space and very little adult supervision, what is not to like?