Hai! This book series is kinda obscure. I’ll tell y’all what it’s about. I’m not sure if there’s a thread for this book series though. It’s about Celtic Mythology and is by Maureen Doyle McQuerry.
Book One Sypnosis:
Beyond the Door, the first in a series from Maureen Doyle McQuerry, weaves a wonderful coming-of-age story with elements of fantasy and mythology. With his love of school and the game of Scrabble, Timothy James feels that the only person who really understands him is his older sister, Sarah, and he’s fairly certain nothing interesting will ever happen to him. But one night, while his parents and sister are away, he sees something that changes everything: mythical creatures in his own living room! Soon, a mystery of unparalleled proportions begins to unfold, and Timothy has to team up with his sister and the school bully, Jessica, in the name of the Light in order to defeat the powers of the Dark. A secret code runs throughout the book that readers can decipher to learn more about their favorite characters and legends.
Book Two Synopsis:
In book two, the excitement and mystery continue as Timothy, his sister, Sarah, and their friend Jessica journey from America to Edinburgh, Scotland, where they seek the Four Treasures of Ireland, especially the Telling Stone. They must keep the treasures from falling into the hands of Balor, who can use them to deprive the world of good. The children pass through Time out of Time as they undertake their quest and encounter a number of mythic and folkloric characters, including the Tuatha Dé Danann, Gwydon, Cerridwyn, and others.

In this book, a code hidden in a map is the key to finding the Stone, and readers work alongside Timothy, Sarah, and Jessica to decode the message. Along with the code, the book includes a glossary of the many historical, literary, and folkloric references mentioned in both volumes.
Characters
Timothy Maxwell
Jessica Church
Sarah Maxwell
Cerridwynn/Ms. Clapper
Star Girl/Electra
Nom
Gwydon
Balor
The Greenman
And Many More!