Funny that you pose this question as I am looking at what I have been using as I read your post. In any event you may want to check out Penguin Guide to the 1000 Best Classical recordings. What I have is a 2011 version so perhaps there is a newer version. The penguin guides used to be very well regarded but now the older versions are dated unless you collect records in which case they still would be useful.
Best single volume guide to classical music
For a Valentine’s Day present. Preferably fun to read. Doesn’t need to get deep into minuscia. At this point in our evolution, I could imagine one with QR codes to take the reader to great performances of pieces. Or a downloadable supplement! But I doubt that exists. Anyhow - thanks in advance.