There are an error in the book with the run_command tag when text command is more than 100 chars length:

1/ If the text in run_command is too long, it is troncated:

Exemple with this book:

/give @p written_book 1 0 {pages:["{\"text\":\"Hello World\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"/say Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft\"} }"],title:"",author:""}

The give command is valid, but when I click in the book, the text is truncated
(see screenshot 1)
The command outside the book work with no problem:

/say Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft

2/ If I use a formatted text, there are an error. I try with the same example as 1/, but with yellow color displayed with a tellraw command:

/give @p written_book 1 0 {pages:["{\"text\":\"Hello World\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"/tellraw @a {\\\"text\\\":\\\"Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft\\\",\\\"color\\\":\\\"yellow\\\"}\"} }"],title:"",author:""}

When I click on the link, the following error occured:

Invalid json: Unterminated string at line 1 column 89

(see screenshot 2)

The command outside the book work with no problem:

/tellraw @a {"text":"Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft Minecraft","color":"yellow"}

(see screenshot 3)

3/ The real problem with this bug is for tools book, it's impossible to make a custom tools book with complex command. For exemple, this book can spawn a zombie with a Full P4 diamond armor:

/give @p written_book 1 0 {pages:["{\"text\":\"Super Zombie\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"/summon Zombie ~ ~1 ~ {ArmorItems:[{tag:{ench:[{id:0,lvl:4}]},id:\\\"minecraft:diamond_boots\\\"},{tag:{ench:[{id:0,lvl:4}]},id:\\\"minecraft:diamond_leggings\\\"},{tag:{ench:[{id:0,lvl:4}]},id:\\\"minecraft:diamond_chestplate\\\"},{id:\\\"minecraft:diamond_helmet\\\",tag:{ench:[{id:0,lvl:4}]} }]}\"} }"],title:"",author:""}

When I click on the link, the following error occured:

Data tag parsing failed: Unbalanced brackets: {ArmorItems:.....{tag:{en

(see screenshot 4)

The command outside the book work with no problem:

/summon Zombie ~ ~1 ~ {ArmorItems:[{tag:{ench:[{id:0,lvl:4}]},id:"minecraft:diamond_boots"},{tag:{ench:[{id:0,lvl:4}]},id:"minecraft:diamond_leggings"},{tag:{ench:[{id:0,lvl:4}]},id:"minecraft:diamond_chestplate"},{id:"minecraft:diamond_helmet",tag:{ench:[{id:0,lvl:4}]} }]}

(see screenshot 5)

The displayed error is always different, for a unique bug.
I report this bug because many users of my book generator report to me this problem, but I can't help them, it's a bug with Minecraft.