The Alluring Specter & Crazy, Reckless, and Rash are the first two books in the Rebuild World series, which uses an unconventional numbering scheme in addition to the rarity of having individual titles for each novel.
Basically they chart the path of a street urchin on his way to becoming an established mercenary as he’s guided by an AI with unknown (though almost certainly nefarious) goals through a post-apocalyptic wasteland. It’s hard sci-fi for the most part with hints of potential romance/harem elements down the line and nothing much to complain about.
The first Moto Saikyou no Kenshi wa Isekai Mahou ni Akogareru book meanwhile is a more common example of a fantasy-to-fantasy overpowered protagonist reincarnation isekai. Said protagonist is overpowered thanks to retaining god-level swordsmanship from his previous life, while the isekai label appears to just be there to provide an excuse for in-character exposition about the setting.
Although nothing to write home about, it doesn’t have any glaring issues and should be entertaining enough for fans of the genre.