Hudson Densetsu 5 is now available for pre-order. This is the latest in a series of books from former Hudson game designer Hiromasa Iwasaki covering every Hudson game on the Famicom and the PC Engine. (1 and 2 cover Famicom; 3-5 cover PC Engine.) Book #5 has apparently caused Iwasaki to look more into the subject of outsourcing (which Hudson did a lot), and he has been able to talk to people from various development companies. He has expressed interest in putting out a revised version of these books.
a little more context on these books: Iwasaki's specifically chronicling the development history of Hudson's games by talking to the people involved with each and every game, and because he has both a personal history with Hudson and the respect of his peers, he's been able to not only interview a ton of people but hit them up for extensive follow-ups and other exploratory conversation, augmented by his own knowledge as both a developer and writer and historian, and the results are as authoritative a history on these games as we're ever likely to get. My impression is that there are certain factors keeping Iwasaki for pursuing a wider release in any language; he's content for things to live on at the Diet, and it's hard to hate on that way of thinking.
(For the unaware, Iwasaki's history in game development started in the mid-'80s: he was involved with the design of the CD-i while in college, and later ran point on a lot of Hudson's higher-profile PCECD games as a programmer, including Ys Books 1&2, Tengai Makyou II, Emerald Dragon and Linda Cube. He was pulling double-duty as a reviewer/columnist during this era, and is widely acknowledged as the first person to publicly go to bat for Tokimeki Memorial, giving it a near-perfect score in Dengeki PC Engine at a time when nobody, including Konami themselves, really thought anything of it.)
Incidentally, Iwasaki's been involved in one of the bigger recent blow-ups in the JP old-game-dork scene: the short version is that Kodansha published a three-volume book touting itself as a comprehensive history of games that was so frequently and egregiously inaccurate that you'd think it was deliberate, written by someone who defended their writing by claiming "facts" and "data" were an outdated idea only valued by an intelligentsia that's on the verge of being superseded by AI, and Iwasaki was a key figure in not only getting the books pulled from circulation but very quickly producing widely-shared rebuttals of the contents of each book. He recently published a streamlined and less off-the-cuff, blog-ranty version of his corrections and commentary as a print book ("A slightly-more-accurate History of Games")—again, this was for the sake of making sure the opposition to Kodansha's books was formally recorded; a big part of the reason he and others were so incensed about those books was because they were being distributed to schools as educational resources.
so, the author of Kodansha's Game no Rekishi series finally returned (via a paywalled note post) to talk about the Real reason their book was pulled: turns out it's not because their book was a complete fantasy that damaged the credibility of Kodansha's editorial department, but because the gaming sphere has been ceded to elitist otaku who wield "historical rigour" as a cudgel to silence the outsider voices that they secretly believe will replace them. Who knew?