The "Gambler Jack" books are scattered throughout Liberl and finding all of them is required to obtain the best weapons in the game. Beware, as some of these are extremely out of the way and have a very short time-frame to acquire.

Item	Location
Gambler Jack Vol. 1	Prologue: After Le Locle is attacked but before setting of for Grimsel fortress, check the rooms upstairs in the Bracer HQ.
Gambler Jack Vol. 10	Chapter 7: After completing Carnelia tower, but before completing Sapphirl tower, speak to Antoine the cat while Kloe is in your party.
Gambler Jack Vol. 11	Chapter 8: After finishing the Rolent sidequests, witness the wedding, then speak to the guests in the bar.
Gambler Jack Vol. 12	Chapter 8: After finishing the Ruan sidequests, speak with the students at the Jenis academy.
Gambler Jack Vol. 13	Chapter 8: After finishing the Zeiss sidequests, head to Wolf Fort and speak with the soldiers there.
Gambler Jack Vol. 14	Chapter 8: After all areas have been cleared but before heading to Grancel, return to Bose. The book-seller is giving it away.
Gambler Jack Vol. 2	Chapters 1, 2, or 8: Purchase from the Ruan casino for 100 medals.
Gambler Jack Vol. 3	Chapter 2: On the airship at the start of the chapter, talk to Olivier twice.
Gambler Jack Vol. 4	Chapter 3: After speaking with the Erebonian Ambassador, but before leaving the Embassy, talk to the librarian.
Gambler Jack Vol. 5	Chapter 3: While searching Grancel for Renne, talk to the patron in the Coffee Shop.
Gambler Jack Vol. 6	Chapter 4: Immediately after arriving in Rolen, go into the building beside the bar and talk to the woman inside.
Gambler Jack Vol. 7	Chapter 5: After killing the three quest monsters at the start of the chapter, talk to the soldiers at the Krone Pass checkpoint.
Gambler Jack Vol. 8	Chapter 6: Before going to the resort, go to Ravennue village. A boy there has it.
Gambler Jack Vol. 9	Chapter 6: Before going to the resort, go to Haken gate. One of the soldiers there has it.
Ultimate Weapon	Chapter 9: Access the terminal in the bar building with the Zemurian Crystal in your inventory. Take the resulting data orb to Russel for your reward.
Zemurian Crystal	Chapter 8: If you have all 14 volumes of Gambler Jack, speak to the NPC on the top floor of the Bracer Guild in Grancel and trade them for the crystal.