For a while I'd been put off doing the Boradsheet crosswords as I felt like Icouldn't speak the "language" the crossword setters would use in their clues, but this book really is like the rosetta stone when it comes to breaking down exactly how the clues are constructed.
The book starts by breaking down the clue types, and how they are indicated and built. Using detailed descriptions of example clues for each type, you'll soon know how to get from the clue to the answer.
As with anything, practice is the key to truly mastering, and this book not only has lots of example clues for you to analyze, but it also contains full puzzles, with full explained solutions, so you can have lots of dry runs before going for the real thing.
Not stopping there, the book also contains a list of commonly used abbreviations, which I found incredibly helpful, as well as a list of indicators (words that point to things like anagrams, sandwich clues, etc within a clue).
After reading the chapter on clues alone, I almost finished the Telegraph crossword the same day! Ok, so I'm not there yet, but this book is an indispensable tool for getting your mindset into that of the crossword solver.
If you are clever enough to attempt the cryptic crosswords, but find yourself frustrated