The Boggart and the Monster by Susan Cooper is a delightful sequel to The Boggart. Emily and Jessup Volnik return to Scotland to visit Mr. Maconochie, the new owner of Castle Keep; Tommy, the local boy they befriended on their first trip; and, of course, the Boggart who gave them so much trouble in the previous book. Mr. Maconochie, who only recently discovered the boggart, is thrilled to find out that the children know all about it (and that he is not going crazy). They decide to take a camping trip with their first stop at Loch Ness where Jessup has been invited by a professor to see his state of the art submersibles that are going to look for the famous Loch Ness monster. The boggart, who accidentally fell asleep in the camping gear, is excited to visit his cousin Nessie who hasn't been seen in hundreds of years. Unfortunately, Nessie has spent those years asleep at the bottom of the loch in her monster form and has forgotten how to change shape. Can the boggart figure out how to get help from Mr. Mac and the children? Will they be able to help Nessie escape the probing submersibles and remember how to be a boggart again?
Another excellent read by Cooper that I would recommend for ages 8 and up. It's a little more serious than the previous book, but still a delightful read for all ages.