Literacy Leveler™ makes it easy to level children's books in your collection and find books of an appropriate reading level. It supports the popular Lexile®, DRA, and Guided Reading leveling systems. It costs $5.99. The one you are interested in is the Lexile level or F&P (Fountas and Pinnell). http://fikesfarm.com/litlev/
Junie B. Jones by Barbara Park
Boxcar Children by Gertrude Chandler Warner
Magic Tree House by Mary Pope Osborne
Flat Stanley
Jigsaw Jones Mystery
Cam Jansen by Adler, David A.
Ivy and Bean by Barrows, Annie.
Roscoe Riley by Applegate, Katherine.
Mercy Watson by Kate DiCamillo
Horrible Harry series by Suzy Kline
My America series (various authors)
Ready Freddy by Abby Klein
Magic School Bus Chapter Book Series by Anne Capec
A to Z Mysteries by Ron Roy
Geronimo Stilton Series
The Hardy Boys Secret Files Series by Franklin W. Dixon
Nancy Drew and the Clue Crew by Carolyn Keene
My Weird School by Dan Gutman
Elephant and Piggie, by Mo Willems
The Diary of a Wimpy Kid series, by Jeff Kinney
Ricky Ricotta’s Mighty Robot, by Dav Pilkey
Judy Moody, by Megan McDonald
Rainbow Fairies, by Daisy Meadows
Babymouse, by Jennifer Holm
Lunch Lady and the League of Librarians: Lunch Lady by Jarrett J. Krosoczka
BONE by Jeff Smith
Henry and Mudge
Mr. Putter & Tabby
Stink by Megan McDonald
Amelia Bedelia by Herman Parish
http://thisreadingmama.com/beginning-chapter-books-series/
https://www.sspl.org/children/booklists/grade2/
http://www.123homeschool4me.com/2014/08/top-25-chapter-book-series-for-1st-2nd.html
http://greatkidbooks.blogspot.com/2011/05/series-we-love-in-2nd-grade-ages-7-9.html