I have searched through the Modding tutorials, including the Wiki, and searched the forums but not come up with an answer to my precise question. I want to increase the Fun on a Maxis object (bookshelf, specifically, since it's criminal that they all only give 1 in Fun!). It's for personal use, so I don't know that I still need to clone it and give it a new GUID - am I understanding that correctly? I must point out that I am the very definition of a modding baby, so please couch any replies as if speaking to one. For example, I've heard of BCons and BHAVs but don't know what they are, nor do I know how to even find an object in SimPE... I downloaded Echo's 'Making Your First Custom BHAV' tutorial and LizzLove's 'How to Increase the Energy Level and Comfort on a Bed', but I'm not sure if they're what I need for this.

Any help would be grreatly appreciated.

Start looking at the Book object not a bookshelf since you can read a loose book from world. Open objects.package from your latest expansion pack.

Book is group 0x7F4B1557 belonging to BookGlobals group 0x7FE64A8D.

Here you have code: "Sub - Start Read Motive Changes" ( 7FE64A8D : 205E )
You could decide to have different motives for what kind of book it is. You can see how some book (presumably Cooking, attrib D == 2) decreases Hunger.

The second line applies to all books equally:
You can see that it refers to private constants of "Book".

This is in BCON 0x7F4B1557 : 1002

Line 0 is the amount of fun gained: 0x2D (decimal 45).
Line 1 is the maximum fun reachable with a book: 0x4B (decimal 75)

So the most simple mod you can make is extracting this BCON into a new package and change the value 0x2D to be higher.

There are a few other possible books, each with private constants. If you modify the BHAV, you can apply to all books. Or you can modify those other books for different fun values.
Book - Novel : 0x7F1B0FBB
Book - Photo Album : 0x7FE57E76
Book - Diary : 0x7F5C21B9

Thanks so much for the response. I hope to check it out this weekend.