I read so voraciously as a child that I was rather stunned when just a couple years ago my husband handed me “I Capture the Castle” by Dodie Smith and I realized I had never seen it before. With an enticing title like that and my sharp-eyed shelf browsing tactics, how could i have missed it? I’ve decided that my hometown library must not have had a copy, and indeed the sole copy they now have is a 1999 printing which lends some small credence to my theory. Now that I am fully acquainted with the lovely tale of Cassandra Mortmain and her family, the BBC has finally translated it to the silver screen. “Buffy the Vampire” fans will take note that Marc Blucas is appearing as Neil Cotton. “E.T.” star Henry Thomas is Simon.