Rob Vollman's Hockey Abstract 2015 Update offers, for my money, one of the best looks at the NHL from an advanced stats perspective you can find on the market.
In its 150-plus pages of analysis, explanation, and insight on the current state of hockey played at its highest level, Vollman—with help from Tom Awad and Iain Fyffe—provides updates on hard-to-find stats and a variety of new material that builds on the template established by the 2013 and 2014 editions of his Hockey Abstract series.
(Publishing note: Vollman's team signed a deal with ECW Press this year, so future editions of Hockey Abstract will be available in bookstores starting in 2016.