As working with others (one-to-one or in smaller groups) is key in peer mentoring, it is worth engaging with theories and literature focusing on group work.
Peter Hartley and Mark Dawson have – a while ago, 2010 – published a Pocket Study Skills Guide on this: Success in Groupwork.
I recommended the book to all those who are new to peer mentoring. The guide is available as paperback or ebook – and is very reasonably priced.
Abstract: Using examples of real students’ successful group projects, this succinct and supportive guide will help students tackle group assignments with confidence. Bite-sized chapters take students from forming a group and establishing roles through to dealing with conflict and delivering a group assessment. The book contains practical advice on making decisions and active listening, alongside opportunities to reflect on progress and identify opportunities for improvement.