Readable, cutesy scifi. Weir writes with the same constipated wittiness of John Scalzi, which unfortunately makes the book nowhere near as good as it sounds.
All the characters are basically the same character, they all speak the same way, and "wow," "noted," "it's a thing!" and "or something" are standard dialog items. This author can tell a competent story but he can't (yet) produce interesting characters.
A reader looking for a significant recent sci-fi work (like Cixin Liu's The Three Body Problem) would be deeply disappointed with this novel.
There is one interesting MacGuffin-type device in this book worth mentioning: by giving his main character amnesia, the author has the magical ability to endow him with any technical skill or technical knowledge he needs: just narrate (or have the main character himself "realize") that he already knew it before. For example, if the main character needs to do a spacewalk, make him already highly trained at it, and then have the amnesiac character say to himself "I must have practiced this a lot." It's an interesting device that gives the author much more flexibility to deal with plotting problems, but it flattens the main character into a type of a Mary Sue (or "Competent Man") with superpowers.