Silvertown, Jonathan (2009).
Wikipedia article on citizen science. Briefly look at the issues that the Wikipedia community decided to cover with respect to this topic.
Haklay, Mazumdar & Wardlaw (2018) Citizen Science for Observing and Understanding the Earth in: P.-P. Mathieu, C. Aubrecht (eds.), Earth Observation Open Science and Innovation, ISSI Scientific Report Series 15, https://doi.org/10.1007/978-3-319-65633-5_4. You can find a copy here.
An article by Raquel Da Cunha (2015) in the ECSITE (the European network of science museums and centres) magazine - Are you ready for citizen science?
For an even deeper understanding of citizen science, you might want to explore the following books, both expressing the experience from a citizen scientist perspective:
Diary of a Citizen Scientist, 2014, Sharman Apt Russell
Citizen Scientist, 2016, Mary Ellen Hannibal
The following edited book includes a collection of papers which are also helpful:
Citizen Science: Public Participation in Environmental Research, 2015, edited by Janis Dickinson & Rick Bonney
The Rightful Place of Science: Citizen Science, 2016, edited by Darlene Cavalier & Eric Kennedy
Citizen Science: Innovation in Open Science, Society and Policy, 2018, edited by Susanne Hecker, Muki Haklay, Anne Bowser, Zen Makuch, Johannes Vogel and Aletta Bonn