Some words are easy to mix up. Can you make the right choice?
There were several similarities / similarly / similar to between the two novels, except one was aimed at a younger market while the other targeted twenty-somethings.
Compared / Compare / Comparing with 15 years ago, home PCs are cheaper, faster, and have a much bigger memory.
The new software program shared some common characters / characterizes / characteristics with those that were already on the market.

There were several similarities to between the two novels, except one was aimed at a younger market while the other targeted twenty-somethings.Compared with 15 years ago, home PCs are cheaper, faster, and have a much bigger memory.The new software program shared some common characteristics with those that were already on the market.