Gotta have the "le." The "A mi abuela" is the part that explains who or what "le" is. Avoid redundancy (which Spanish does like) by leaving off the "a" part if it is not needed. "Me gusta" is enough, since you know that "me" means me, so I don't say "A mi me gusta." But I cannot just say "A mi gusta."
Tengo una pregunta...I understand that the "le" is referring to the indirect object (mi abuelo), but I'm not sure when you actually need to use an object pronoun like "le". At first I thought you needed to use a lo/la/le etc. for all indirect/direct objects, but then I came across sentences like "Él ayuda a su madre" (http://www.duolingo.com/comment/245505) where "su madre" is the direct object but there's no la before ayuda. Or even with "Leo un libro," "un libro" is the direct object, but there's no lo before leo. So then I was thinking you only use the object pronouns lo/la/le etc. for objects that are pronouns (él, ella, etc.) and not nouns because all of those kinds of sentences I've seen always have the object pronoun words. But then I come across a few sentences like this where the object is a regular noun "mi abuelo" but the "le" is necessary. Is it just that there are a few verbs that are exceptions and need the object pronouns whether or not the object is a pronoun or a noun while most only need them for pronouns? Could someone please help me with the rules for when to use and when not to use the object pronouns? --- ¡Muchas gracias! :)
Yes, there is a list of Spanish verbs that take the indirect object pronoun. Google "verbs like gustar" for a full explanation. Me gusta does not literally mean "I like", rather it means "it is pleasing to me". The sentence above is literally translated as "To my grandfather, to him it is pleasing", a bit of a mouthful I agree, but once you start to think of it like that it makes sense - and that's what the "a" at the beginning is for, it means "to".
To add to the confusion, there is also a redundant pronoun used when the DIRECT object of a sentence precedes the verb. To use a duolingo example from elsewhere on the site: "Esta bicicleta la usa mi hermano" - "my brother uses this bike" or can be translated with the passive construction "This bike is used by my brother". When the DIRECT appears after the verb, the redundant pronoun is not use as in: "mi hermano usa esta bicicleta"
Ooops. ;) The 'a' in "A mi abuelo le gusta leer" is not the personal 'a' It is the prepositional 'a', meaning 'to.' 'Mi abuela' is an INdirect object and 'reading is pleasing "to him." The personal 'a' is for use before direct objects that are people or beloved animals. Gustar and its relatives take INdirect objects.
mi is not me here it is my, so the person is "mi abuelo" and the "a" refers to him (the personal pronoun required in Spanish but not English). I think if you want to say "My grandfather reads to me" you would need "a yo" in there somewhere, but I'm not sure exactly where. I put the same as you, but it's wrong because we have used the "mi" twice in the translation.