I can join in endorsing Madhur Jaffrey. She's good for the beginner as she makes it fairly simple for the home cook - no arcane equipment required and ingredients available in any Morrison's/Sainsbury's (name your own supermarket) and good greengrocers. A lot of the recipes come from her childhood.
Pat Chapman has been at the curry "game" for donkeys' years. He has run the Curry Club since the 1980s.
Here's the CC website - Home - Pat Chapman's Curry Club
Cyrus Todiwala gets some good reviews (from "real" Indian contributors to Amazon.) but I haven't tried any of his books, however, some of the reviewers say he's not for the beginner - whatever that's supposed to mean.
(If you want to cheat or need curry-in-a-hurry Patak's sauces aren't bad. Not the real home-made stuff but passable - I have an Indian friend who keeps them in for emergencies)