My dd, aged 9 1/2, has just devoured all 15 of Enid Blyton's mystery set books and has asked me for more 'similar' books. She's already read most of Blyton's other sets (Famous Five, Secret Seven, Mallory Towers, St Claires) and love them all. She's particularly interested in more 'mystery' type stories.
Any suggestions for similar mystery books suitable for a 9-10 year old?