How we research books

The bibliographic record for every one of the 65 books on this site — ISBN, edition, page count and list price — is verified against an authoritative source. For Japanese-published books that is NDL Search, the catalog of Japan's National Diet Library, and prices are the list prices printed on the book (本体価格), before tax. For internationally published titles — where library records can describe stale revisions, because some publishers reuse ISBNs — we verify against the publisher's own catalog instead, name the exact revision covered, and list the publisher's price in its own currency. Where the source has no record of a figure, we leave the field empty rather than guess.

Editions are distinguished explicitly. A revised So-matome volume is not the same product as the one described on a decade-old page, so every book record states the exact edition and publication year it covers. When a publisher revises a title, existing coverage is flagged until the new version has been checked.

A catalog lookup, an official sample and months of study are not interchangeable forms of evidence. Each book sits in exactly one of these states, displayed on its page:

Catalog entries can answer objective buying questions: which edition an ISBN identifies, the Japanese list price, what the publisher says is included, and where the book can be bought. They do not claim that we enjoyed the explanations, completed the exercises or experienced a score improvement.

Guides and comparisons may combine those verified facts with official samples, publisher documentation and clearly attributed learner reports. Series-level advice is labeled as such. We never turn someone else's experience into a first-person claim, and an unsourced popularity claim is not evidence.

A detailed standalone verdict is reserved for in-depth analysis. It leads with who the book fits and who should not buy it, followed by the evidence behind that judgment.

Recommendations are never influenced by affiliate commissions. The commission is broadly the same whichever book you buy — and nothing at all when we tell you to skip a purchase, which we do routinely. How the money works is spelled out in the affiliate disclosure.

This site is written by one person, not a panel of experts, and it claims no credentials beyond the sources and evidence shown on each page. More on that on the About page.

When we get something wrong — a price, an edition, a source attribution or a judgment that did not survive stronger evidence — we fix it and leave a note when the correction is substantive. Spotted an error? Write to the address on the About page.