Maintain low accountability

Excerpt from Self-Selected Pleasure Reading and Story Listening
for Foreign Language Classrooms 
by Beniko Mason.Full text here   

Minimum accountability is required. Students can be asked to keep a reading log, but it should be very short. The reading record (the amount of reading) should not be used as part of the evaluation
(grades). When the amount of reading is considered for giving grades, students read books with more pages, which are often more difficult for them. Students’ self report on the amount of reading
may not be trusted. It is not the quantity of pages, but the quality of reading that affects improvement.

A few times a year for evaluations, I recommend the following reading and writing test. Have students read a text for thirty minutes, and ask them to write a summary of the story, including as much as they can remember, in English (the target language) without referring to the text. The students’ writings can be evaluated both subjectively and objectively (Mason, 2004).  Even though students do not engage in writing activities during the reading program, you will be amazed how much they produce and how well they write without any writing practice, grammar teaching, or error correction.

Readers Logs

Have students track the books read. Also interview with students during reader's conferences.