I keep all my old book and they now occupy a whole section of my bookcase.
Most books contain still very useful info and only things like hotel or restaurant reviews might be out-dated.

I even have a copy of Europe on $5 and $10 a day. It make real interesting reading like how to get tickets for for Theatre Royal Haymarket 40 pence ( most expensive seats were $5.00) and admission to the Tate or National gallery was 10 cents.
Included also a four course meal at a "great"
Venice restuarant one block from St Marks for $1.70.
mike