Ms Lewis (and her previous co-author, Thomas Kibling) have been producing revised editions of this book for several years now.
Let me say right off the bat, I am directly involved in representing UK workers in employment law situations and this book has been my single greatest asset. I have been very successful over the years and I owe Ms Lewis' book for that. It is accessible (I am not a lawyer); practical and thorough. Not just that, it is inspirational. Several times it has been the springboard for me to approach cases in new ways. It is full of sample letters and advice on how to write to employers or tribunals; how to gather evidence; what to look for; what the key points of law in each area are. Absolutely invaluable.
Look out for other stuff she or the Legal Action Group may produce as it is all sound and practical advice. Be mindful of the date of publication as each edition is substantially updated.
If you represent UK workers in employment situations and you are serious about doing a good job - BUY THIS BOOK. It's THAT good.