Sir Arthur Conan Doyle & A L Stringer 
Sherlock Holmes in Simple English: The Blue Carbuncle [EPUB ebook] 

A valuable diamond has been stolen, and Holmes and Watson find themselves on a chase through the streets of London at Christmas as they search for clues.
This book is a graded reader. The story has been retold in modern English for students of English as a foreign / second language at intermediate level (CEFR B1) and younger native speakers.
Features
•  Comprehension and vocabulary tasks
•  Summary of the story
•  Endnotes for difficult words, place names and cultural references
•  Word list at the end of the book