I read through Reprisal thinking of it as "Lissle" or "Lizzle" in my head, always wondering how accurate that was.

According to babynamespedia it's pronounced "LAYahl" but I thought of it as you did: "Lissle".

The German name Liesl is pronounced exactly how it looks (rhymes with diesel; see: Sound of Music), and it's a nickname of Elizabeth. Not sure if Paul meant Lisl to be pronounced differently, or why he chose that spelling, or what nationality the character is--it's been a while.

In my head it's always rhymed with diesel. I came across the name somewhere in the Mesozoic period and it stuck with me.

When she discovers poor Ev drunk in the bar, he calls her "Lee-shul" so I always assumed her name rhymed with diesel (when sober, anyway).

Lisl is short for Elisabeth.
In german you say it a little like "diesel", except that you try to go directly from the soft "s" to the "l".
Diesel Lisl is the best one can do when in "english mode".