I have heard that ADHD is hereditary, so it might make sense to have a professional take a look so that you are not spinning your wheels using a squirt gun to put out a fire! On the other hand, I am also all for basic good advice and having read literally hundreds of parenting books, the first two that come to mind (that would be great for ANY parent in almost ANY situation) are
1) Harvey Karp's "The Happiest Toddler on the Block". It gives great ideas on immediately and simply handling tantrums in a way that communicates to your child and makes them feel heard, and therefore they get over it way more quickly! A main technique is matching the toddler in tone, intensity and message in a *SYMPATHETIC* way, until they notice that you get it (usually a few seconds) and then telling them why it is not possible.
Example: "DON'T WANT DON'T WANT DON'T WANT TO LEAVE!! I KNOW YOU DON'T WANT TO LEAVE!!!", over and over until they feel heard and start listening to you. "But we are going to leave to park now so we can go have dinner." I saw the video (which I rented from Netflix) so if you don't have time to read a book, you could just check out the 69 minute video from your library or videostore if they have it.
The benefit of this is acknowledging the toddler's feelings instead of just ignoring it or distracting her/him, which sends the wrong message that their feelings don't matter -- otherwise, they are taught to be out of touch with how they feel (which is a major problem for many adults). This is a major tool in promoting emotional intelligence! But also there are many other important concepts such as 'feeding the meter', 'avoiding trouble situations', 'routine and play', 'teaching patience', and much more that make this book and video worth examining in full.
2) The second book I'd recommend is: "How to Talk So Kids Will Listen and Listen So Kids Will Talk" by Adele Faber and Elaine Mazlish -- this is the one parenting book in general I would recommend if a person could only read one parenting book ever. Once again, it is about understanding how the other person thinks and feels so you really 'get' each other. I think this is the singularly most important skill to know in raising a child because it creates a sense of security as well as covering most bases of life troubles and preventing many problems from getting out of control.
This is just what I've found to be helpful, but I hope it can help you in some way. Good luck!