Since it's early 2018, I will treat the benchmark as 2007, but here are the books and/or articles I got the most from, and that anyone doing work on Nietzsche should have read and thought about seriously during the last decade. These are in alphabetical order.
Jessica Berry, Nietzsche and the Ancient Skeptical Tradition (Oxford University Press, 2011). I was not ultimately persuaded by Berry's ambitious thesis, but the book is a model of how to think about Nietzsche in relationship to ancient Greek philosophy, and displays a masterful command of both.
Maudemarie Clark & David Dudrick, The Soul of Nietzsche's Beyond Good and Evil (Cambridge University Press, 2012). Another book I have many disagreements with (I discuss some of them here), and even if you share my worries, there's still a huge amount to learn from the detailed analysis of the preface and first chapter of BGE and the many philosophical issues raised.
Christopher Janaway, Beyond Selflessness: Reading Nietzsche's Genealogy (Oxford University Press, 2007). I am sympathetic to many of the arguments here, though was somewhat mystified by his mischaracterization of my treatment of Nietzsche's naturalism; our views are in fact rather close, once the confusions are cleared up. Almost every chapter has something to teach the reader, including the specialist. (I reviewed the book here.)
Nadeem Hussain, "Honest Illusions: Valuing for Nietzsche's Free Spirits," in B. Leiter & N. Sinhababu (eds.), Nietzsche and Morality (Oxford University Press, 2007). Beautifully done exploration of "fictionalism" in Nietzsche's metaethics, though one should also see Hussain's later view ("Nietzsche's Metaethical Stance," in K. Gemes & J. Richardson (eds.), The Oxford Handbook of Nietzsche ), which is more skeptical about whether the textual evidence demands supports ascribing a particular semantic view to Nietzsche.
Paul Katsafanas, "Nietzsche's Philosophical Psychology," also in Gemes & Richardson (eds.), The Oxford Handbook of Nietzsche (2013). This deservedly influential paper has become the standard point of reference for thinking about Nietzsche's "drive psychology," and needs to be read by everyone interested in issues of moral psychology in Nietzsche.
Mattia Riccardi, "Inner Opacity: Nietzsche on Introspection and Agency," Inquiry 58 (2015): 221-243 and "Nietzsche on the Superficiality of Consciousness," in M. Dries (ed.), Nietzsche on Consciousness and the Embodied Mind (de Gruyter, 2018). Both of these brilliant papers, which combine scholarly care and erudition with philosophical sophistication, have shed new light on Nietzsche's arguments for epiphenomenalism about consciousness. I eagerly await the book manuscript on Nietzsche's philosophical psychology that Riccardi is presently completing and which will surely become a classic in the secondary literature.
Donald Rutherford, "Freedom as a Philosophical Ideal: Nietzsche and His Antecedents," Inquiry 54 (2011): 512-540. This is the best paper on the vexed question of Nietzsche's understanding of "freedom," tying it convincingly to the kind of view one also finds in Spinoza, one in which determinism or fatalism is reconciled with a rather different notion of "freedom" than one finds in the Humean or Kantian traditions in the modern era.
Tamsin Shaw,"The 'Last Man' Problem: Nietzsche and Weber on Political Attitudes Towards Suffering," in M. Knoll & B. Stocker (eds.), Nietzsche as Political Philosopher (de Gruyter, 2014). This extremely suggestive paper elucidates part of what Weber found so significant about Nietzsche, and in the process sheds light on a central Nietzschean concern, the affirmation of life not in spite of, but because, it involves suffering. (This paper was the original stimulus for my own take on these issues in Nietzsche.)
Now that's only 9, not 10, books/articles, and I'm not sure I could single out a 10th as helpful and important as these papers have been for my own work. Readers are invited to suggest their own; include your full name or your comment will not appear, and please state the reasons you found the book or article especially illuminating. Anything with a publication date of 2007 or after is eligible.