Every abandoned reading journal died the same way: it asked for more effort than the reward justified. Ten fields per book is a chore. One line per book is a habit. Start smaller than feels worthwhile.
Record the thing you'll actually want later
Not the plot — you can look that up. What you'll want in three years is what it did to you: where you were, what you were going through, the line that stopped you. That's the part no summary anywhere will give back.
Plot is recoverable. Your reaction isn't. Record the reaction.
Three formats that survive
The one-liner. Title, date finished, one sentence. Takes nine seconds and is enough to rebuild a whole reading year. The quote book. Only lines you loved, no commentary. Becomes strangely moving to reread. The letter. After a book that mattered, write two paragraphs to nobody about it. Rare, slow, worth far more than the others.
Pick one. Combining them is how people end up doing none.
Rate honestly or don't rate at all
Star ratings are only useful if they're for you. A five for a flawed book you adored is more informative than a technically-correct three. If you find yourself rating for an imagined audience, drop the numbers entirely.
Write while you're in it, not after
Notes taken mid-book are sharper and more honest than a tidy retrospective written a week later, when the ending has flattened everything before it. This is the same reason margin notes beat summaries — more in how to annotate books and how to remember what you read.
Keep it next to the book
A journal in a separate notebook or app gets orphaned — the note survives and the sentence that caused it doesn't. On Arwy notes attach to the exact line inside the book, so they're still there on a reread, and you can see what other readers wrote in the same margin.
Keep your notes on the line that earned them. Try Arwy.