By the book

As a detective trying to solve the mystery of the crossword clue ‘By the book‘, I had to consider multiple possibilities. However, my first instinct was to think about the common use of the phrase ‘by the book‘ in everyday language. It usually refers to following the rules or laws strictly without deviation. From this initial insight, I began to explore words that could fit the definition, perhaps something like ‘conventional‘ or ‘orthodox‘. However, the more I thought about it, the more I realized that the most fitting word would be ‘lawful‘. It is the most direct synonym for ‘by the book‘, and it perfectly aligns with the definition. The word ‘lawful‘ implies a strict adherence to rules and regulations, which is precisely what ‘by the book‘ entails. With this conclusion, I was confident that ‘lawful‘ was the answer to the crossword clue.