"Imouto sae Ireba Ii" (all good as long as we have younger sister) volume 1 by Hirasaka Yomi. You can probably guess how it ends from the just title and the cover illustration, and all pages in between are merely fluff. Very entertaining high quality fluff.
The book revolves around a novel writer with fanatical interest in younger sisters, and has a younger step sister brother. The book opens with a few pages of what such a writer might produce, and it's definitely for a much more niche audience than the rest of the book. Majority of the book are anecdotes of how novel writers work, which are mostly reasonable events (such as calculating income tax) interleaved with spurs of unusual actions (such as trying to claim in-game purchases for tax deductions). It's this mixture of realistic and unrealistic bits that makes this book easy to relate to and enjoyable at the same time.
I read this book first before following recommendations to read "Eromanga Sensei", since both happened to be novels about novel writers. The novel setting is about all the overlap there is between the two series, the content and style are completely different. If "Eromanga Sensei" was a full course meal, "Imouto sae Ireba Ii" is all desserts. The reason why this book feels fluffy is that the events and characters aren't really strongly connected, some chapters can probably be shuffled or dropped without readers noticing much loss. This style is consistent with the author's previous series (Boku wa Tomodachi ga Sukunai). It's neither good or bad, it's just meant to be enjoyed with a different mindset.
While I wasn't expecting a deep central story, the first volume did end in exactly the way I expected. This should be an interesting series to follow.
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Next (2015-11-09): Fernando Sor