Trying to work with illustrator to make some simple icon illustrations for a book.. anyone have any tips for this sort of thing? I'm useless on AI so i need to brush up. i can see somethings missing here (other than colour) but what?;/

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They're not bad, maybe a little "flat" but certainly OK to use. I think maybe one thing I would look at is the strokes - the simple lines are maybe making them less eyecatching than they could be. If you after simple icons then I think you have achieved that; if you are going for something more appealing then maybe think about using a very light grey as shading and giving them a bit mroe form?