My cat is afraid of bos

And look at paragraphs 4 and 5 on the website. It says it can have a vessel such as a cat(or a person as paragraph 5 states)

Familiars are not pets.
Whoever told you they are, is misleading you.

Thank you for telling me everyone. There seems to be a lot of confusion when it comes to magick

As already stated above; familiars are spirits that often times resemble animals but are not actual animals.

The person who told you that must have gotten too excited of the idea of having a familiar and misunderstood what they really are.

While animals can be trained to do tricks, accompanying you in your practice is a different story. They have good senses that allows them to notice what the human eyes may not, but that is just it.

I am not going to bother to restate the Familiar fact, it's been said enough.

Now, 'Why is my cat having a fit when I take my book out?' could be several reasons, the most likely could be the smell of the book - if you've been around a lot of incense etc some cats don't like it and become distressed at the scent.
Could be perhaps they have noticed the shifts in your body, the subtle movements etc that you go through when you're working with your book (Body language)
Now, in terms of the Occult/Paganism/Magic/Whatever else you want to call it, there is a long held belief that animals can see more than we do - they feel the vibrations of the world around them - so perhaps as one stretch as to why could be the lovely fact that your cat has noticed 'shapes or something' around your book or around you when you get involved with your magic - what I mean is that people believe that cats, dogs etc can percieve spirits (This is to explain why dogs bark at nothing, or cats get skittish and run off in a hurry for no known reason that we can see/observe)

Ya, there was no incense in my home or anything. And it could have been micromovements. But it might be because I've tried to make a sigil to protect my book from things such as people taking a peep into it. Also, since I have no other place to put it, I put my tarot cards(hand made) in there.

Familiars CAN be physical animals, they aren't necessarily spirits all the time. And yes, it's also common that your familiar also happens to be your pet.

Wiccanery, they are not physical animals/pets. The end

You know you're all allowed to have different beliefs. Actually- it's apart of the guidelines for this forum! If wiccanery believes that a cat could be/become a familiar- respect that. Do not push your belief on to others. This is silly and disrespectful. Accept that they don't agree and move on.
And to Wiccanery's benefit, there other forms of witchcraft and religions that dictate that physical animals can be familiars, vessels, etc so even if yours does not, that's okay.