Every gateway apologetics book has a thematic approach that guides the reader. With Lee Strobel, it's the journalist approach; with J. Warner Wallace, it's the approach of the detective. Murray's approach is an interesting double-barrel: He is both an attorney AND a former Muslim. So I don't have to tell you why this is a good volume in terms of the author's qualifications.
What I do have to tell you is that this book is more of a philosophical gateway than a "hard evidence" gateway. As the title implies, Murray approaches his topics in terms of "big questions." I'm not as much an expert on these issues, but I'd say based on the presentation and sourcework that Murray's book would be an excellent one to present to the earnest seeker. Give it a shot.