We've read
Railway Children, Phoebe the Spy, and
Key to the Treasure. We enjoyed them all, and they are all very different from one another. I agree that
Railway Children requires a more seasoned listener, but good living books often do, especially as dc get older. I like to give books time to grow on me and our dc, as these are often some of our favorites by the end. We had this with
King of the Wind, Railway Children, A Lion to Guard Us - many books that are now among our favorites. It has taken me awhile to recognize and love living books, but it has been worth it. We actually just have been having this with
Mountain Born, and now that we are more than halfway through, we are loving it. The character development and plot development has grown and grown - we can now see the parallels to the Biblical character David, and to our Lord and Savior Jesus. This is just fresh on my mind as I was thinking today I was so glad we continued to read and now are enjoying it so much. So, while it's wonderful to have lots of options of books to read, I'd like to encourage you give book selections a due period of time for a good while first before making a change, as this allows for a story to truly develop, and for a more classical way of writing to grow upon us.

This will be incredibly important as our dc get older, so when they are doing classical works such as Shakespeare's or reading
Pride and Prejudice - they can enjoy these works and not be totally shocked at the change. Just food for thought, as this is a journey I've been on my past 15 years of teaching too. Since you've already made the decision to put aside the
Railway Children, both
Phoebe the Spy and
Key to the Treasure are shorter in length, have much shorter, less complicated sentence structure, and are very enjoyable to read and listen to, so either one of those books would be wonderful as well.
In Christ,
Julie