'Mentoring in the early years’ by Alison Robins, published by Sage Publications Ltd.

Read: Chapter 1 ‘What is mentoring?’
Chapter 2 ‘The mentor as the one in the middle’
Chapter 3 ‘Being reflective: Encouraging and teaching reflective practice’
To note, this book was written before the revised EYFS was published in 2014 so there may be references to out-of-date legislation.
NB You do not need to buy this book. It may be available to borrow at your local library service, or online.