If you'd like to be able add new notes/notebooks, or update existing notes/notebooks in your Evernote account(s) from your IDE, then buy Spellbook. When you buy Spellbook you'll be able to add new notebooks, update notebook names, add new notes (using Markdown or the built in Spellbook editor), update existing notes (using Markdown), and tag notes right from your IDE. Spellbook Basic only allows you to VIEW content in your Evernote account. You will not be able to add new notes or notebooks, tag notes, or update existing content in your Evernote account.
If you have lots of note content and need to be able to quickly find the notes you need, then buy Spellbook. When you buy Spellbook you'll be able to use advanced search filters, including the use of wildcards and phrases as well as full text search on note titles and note content. These advanced filters let you perform more complex searches on your accounts to narrow the search space and easily find the exact content you want when you need it.
If you have multiple Evernote accounts to stay organized, then buy Spellbook. When you buy Spellbook you'll be able to access ALL of your accounts simultaneously, even from multiple IDE instances! Spellbook Basic only allows you to access ONE Evernote account at any one time.