I looked for the same one and even donated. But as far as I know there is no book yet.
https://www.okpal.com/building-user-interfaces-with-spec/?utm_campaign=01DKKYM06QR7GF0K4S5YA3VVZ0&utm_medium=campaign_edit-okpuid_01DKKYKZ99J5VPEAKHNXH8375A-20190903&utm_source=share_directlink#/ -Joerg -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html
