～やすい

～やすい goes on the ます-stem of a verb and means "easy to do": かく書く becomes かきやすい書きやすい, "easy to write with". The thing that is easy comes first with は or が, not with を.

• × この本を読みやすいです → この本は読みやすいです
• × 読むやすい → 読みやすい

The result is an い-adjective and changes like one: よみやすかった読みやすかった, よみやすくない読みやすくない, and before a noun よみやすい読みやすいほん本.

"Easily", "tends to"

With a verb that nobody does on purpose – slipping, breaking, catching a cold – ～やすい means that it happens easily: "is likely to", "tends to".

～やすい and ～にくい

〜～にくい is the opposite, "hard to do", and goes on the ます-stem in the same way.

The ～やすい here is not やすい安い, "cheap". The two sound the same, but ～やすい is always written in kana after a verb.