Reading of datasheets is or should be an important part of designing electronic devices. Reading datasheets is necessary for writing device requirements, planning budget, and selecting suitable components. Datasheets of each component may be found in manufacturers website.
Once you’ve selected a suitable component, be sure that you read the datasheet and understand everything in it. Otherwise, you may miss some critical parts that could ruin all your plans. It is better to find errors before you start designing than after.
Another important issue is that always check for newest datasheets and errata – datasheet bug lists. It is not good practice to use your old datasheets from your hard drive archive or other places. These datasheets may contain bugs.
Just download the newest microcontroller or other semiconductor datasheet and compare to yours downloaded let’s say a year ago. Errata’s and datasheet changes are usually listed at the end of the datasheet. You may look at this and find out what would you miss with old datasheets. The electric characteristics maybe are the same, but there may be configuration bugs or even discovered bugs in hardware and proposed workarounds to avoid them.
So be critical and don’t rely blindly on everything. Always double-check.