Any tool in the arsenal is always a good thing. I have been using an awesome free app lately worth checking out. The App is called Key Collector Comics and it is a very robust data base of key books and character first appearances. It is available on both Apple and Android platforms. The App has a 5 star rating kn the Apple Store.
I had a chance to talk to creator Nick Coglianese. He has been working on the database for years and has put a lot of time and effort into the project.
You can check it out at Key Collector Comics Website for more info and a free download.