Not exactly a diary, because it was written in an occasional sort of way, on index cards. Most entries are only a sentence or so. The book is a chronicle of Barthes' grief following the death of his mother. The fragmentary nature -- though I found myself reading it compulsively, rather than in slow, reflexive fashion -- means that rather than a sense of wallowing or self-indulgence, you have the idea of an iceberg of sorrow thinly covered by a veneer of day-to-day coping, with this book being a kind of ice pick chipping at the mass beneath. It's quite moving, though not a work I found myself relating to (the way you absolutely do -- or at least I did -- to Joan Didion's Year of Magical Thinking.
I picked this up after reading Michael Taussig's I Swear I Saw This, which is an extended reflection on the field notebook as a genre. He entertains the idea of it as a modernist text, and is specifically interested in the role drawings play. I was not particularly taken with his thoughts on drawing -- overall, many of his ideas seemed somewhat derivative, though at least he gives plenty of credit to people like Barthes and Benjamin -- but the idea of the notebook as a fetish, and of anthropology as a space of contact rather than observation, I really enjoyed. Both the Taussig and the Barthes were useful to me as works that reflect on the process of writing, helping me get over my own strange blockage about it.